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Biology Dictionary

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Test Cross Definition

The test cross is an experiment first employed by Gregor Mendel, in his studies of the genetics of traits in pea plants. Mendel’s theory, which holds true today, was that each organism carried two copies of each trait. One was dominant trait, while one could be considered recessive. The dominant trait, if present, would determine the outward appearance of the organism, or the phenotype . Thus, Mendel became interested in the question of determining which organisms with the dominant phenotype had two dominant alleles, and which have one dominant allele and one recessive allele. His answer came in the form of the test cross.

The purpose of the test cross is to determine the genetic makeup of the dominant organism. Mendel wanted to do this so that he could be sure he was working with a dominant organism which was homozygous , or contained only dominant alleles. However, the phenotype alone doesn’t not tell you the genotype of an organism. The organism could be hiding a recessive, non-expressed allele. To find out what this unknown allele was, Mendel developed the technique of breeding this individual with a homozygous recessive individual for the same trait.

The phenotypic results of the offspring then tell you the genetic make-up of the original parents. The recessive phenotype parent is known to have two recessive alleles for the trait, otherwise the dominant trait would show. If the dominant phenotype parent has a recessive allele, this will be given to approximately half of the offspring. These offspring would receive a recessive allele from the other parents, and therefore be homozygous recessive. Thus, if any of the offspring from the test cross have the recessive trait, the dominant phenotype parent was actually heterozygous , having both a dominant and recessive allele.

If, on the other hand, the offspring all show the same dominant phenotype as the unknown parent, then the second allele the dominant phenotype parent has is also dominant. The recessive parent had to donate a recessive allele, either way. Thus, every offspring has at least one recessive allele. If none of the offspring show a recessive phenotype, it means that the dominant parent passed only dominant alleles to the offspring. This would make the unknown parent a homozygous dominant individual for that trait. In other words, the test cross is a genetic test which reveals the unknown genotype of dominant individuals. The test is interpreted through the number and type of offspring. Below are some common examples.

Test Cross Examples

Monohybrid cross.

The typical example of the test cross is the origin experiment Mendel conducted himself, to determine the genotype of a yellow pea. As seen in the image below, the alleles Y and y are used for the yellow and green versions of the allele, respectively. The yellow allele, Y, is dominant over the y allele. Therefore, in an organism with the genotype Yy, only the yellow allele is seen in the phenotype. Mendel had a yellow pea, and he wanted to know whether it was YY or Yy.

This was important to Mendel as it is to many seed producers and farmers today. The quality of a seed is determined by the plant it produces. A YY plant, if self-fertilized, would produce only yellow peas, in all of its offspring. There are many traits which are desirable to reproduce, and a homozygous plant is the obvious choice to do reproduce it with. However, in a dominant/recessive relationship, it is impossible to distinguish between a homozygous dominant plant (YY) and a hybrid, or heterozygous plant (Yy). Both would produce yellow seeds. However, if the Yy plant self-fertilizes, there is a chance of an offspring with the (yy) genotype, which would make green peas. Mendel sought to sort this out once and for all, so he devised the following test cross.

Mendel bred the unknown yellow pea (Y?) with a green pea, being homozygous recessive (yy). The chart below shows the two possible outcomes of the test.

Test Cross

Either the offspring would be all yellow, or around half of them would be green. This is based on the results of the two Punnett squares shown. The top square shows the results if the unknown yellow pea is (YY). In this case, the pea has no recessive allele to pass to the offspring. Therefore, 100% of the offspring receive one Y allele and one y allele, making them all yellow.

In the second case, if the unknown yellow pea has the genotype Yy, half of the offspring will receive this allele. The other allele will be from the green pea, and will also be a green allele (y). In this case, half of the offspring will produce green peas. The test cross itself occurs when the two plants are bred together, by taking pollen from the recessive plant, and carefully placing it on the flowers of the yellow pea plant. Mendel would then carefully rear all of the beans produced (which would be yellow) into plants of their own. The color of peas that these plants produced would determine the genetics of the original plant, which produced the yellow (Y?) seeds.

Dihybrid Test Cross and Beyond

This simple model works well for a single trait, but it can easily be expanded to encompass more traits. The dihybrid cross is a cross which looks at the cross of two separate traits with different alleles. Sticking with the pea color example, we will add a trait to the cross, let’s say shape. Peas can either be round and plump, or wrinkly. Round peas are dominant, created by the (R) allele. Wrinkled peas are only found in homozygous recessive individuals (rr). The following chart shows how to calculate the results of test cross. (Note that wrinkled seeds should have the r allele).

Dihybrid Crosses

In the case shown, this is a test cross involving an individual which is homozygous dominant for both traits, with the all recessive test cross individual. This test cross individual will always have all recessive traits, as it allows for immediate detection of the genotype based on the offspring ratio. The image describes using the FOIL method of determining all the possible outcomes. On the first genotype, you would pair the first allele of each gene (RY), then the outside pair (also RY). After carrying this procedure out, you have all the possible gametes formed from each parent. Eliminate the repetitive pairs, and you have the only relevant pairs. In this case, all of the offspring are going to be RrYy. This would tell us that the parent was homozygous dominant for both traits.

If the first parent was heterozygous for both traits, the ratio of phenotypes would look much different. In this case, the first parent would be (RrYy). Using the FOIL method, you arrive at 4 possible gametes from the heterozygous parent: RY, Ry, rY, and ry. Combined with the single gamete type produced by the test cross parent, you can get 4 possible genetic combinations. These are RrYy, Rryy, rrYy, and rryy. The ratio on the bottom would be 1:1:1:1.

Thus, if you had a plant which produced round and yellow peas, but knew nothing else about it, you could put it through a test cross with a wrinkled green plant and know, for certain, the genotype of the original plant. While Mendel was limited in his day, the math of these crosses can be analyzed by computers much faster than humans can fill out Punnett squares. Thus, any number of traits can be analyzed by complex functions, with simple inputs such as color and shape. This has taken much of the guesswork out of genetics. However, many genes do not function by simple dominant/recessive relationships, and are controlled by much more complicated mechanisms.

Hartwell, L. H., Hood, L., Goldberg, M. L., Reynolds, A. E., & Silver, L. M. (2011). Genetics: From Genes to Genomes. Boston: McGraw Hill. Lodish, H., Berk, A., Kaiser, C. A., Krieger, M., Scott, M. P., Bretscher, A., . . . Matsudaira, P. (2008). Molecular Cell Biology (6th ed.). New York: W.H. Freeman and Company. Widmaier, E. P., Raff, H., & Strang, K. T. (2008). Vander’s Human Physiology: The Mechanisms of Body Function (11th ed.). Boston: McGraw-Hill Higher Education.

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Microbe Notes

Microbe Notes

Test Cross (Single, Two, Triple Gene)- Definition, Examples, Uses

Phenotypic characters can be easily separated just by looking at the individual. It’s not that easy to determine the genotypic character of that same individual. This is because, genetically a dominant character can be either homozygous or heterozygous, and it is impossible to separate them just by looking over phenotypic characters.  To determine the genotype (homozygous or heterozygous), Mendel developed a genetic cross method, known as “ test-cross ”.

A test cross is a very important genetic tool devised by Gregor Johan Mendel.  It is applicable in Mendelian genetic characters only, but not in non-mendelian genetics. 

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Test Cross Definition

A test cross is a genetic method for determining the unknown genotype of a dominant individual. It is a breeding method between a (known genotype) homozygous recessive individual with an individual of the opposite mating type with an unknown dominant genotype.

Generally, dominant offspring is crossed with a known recessive parent or another recessive individual to determine the genotype of the offspring. Hence, it is a type of backcross. Alternately, it can also be used to determine the genotype of dominant parents also.

The resulted offspring’s phenotypic characters are studied and the genotype of the tested individual can be determined accordingly. If all the offspring after the test cross are dominant, then we can say that the genotype of the tested unknown individual is homozygous dominant. Whereas, if 50% of offspring show dominant and the rest 50% show recessive characters, then we can say that the genotype of the tested unknown individual is heterozygous dominant.   

Based on the number of genes or characters studied during the test cross, we can categorize the test cross into monohybrid test cross, dihybrid test cross, trihybrid test cross, and polyhybrid test cross.

Test Cross Types and Examples

A. Monohybrid Test Cross   (Single Gene Test Cross)

Also called ‘single gene test cross’, is a type of testcross where only one type of gene or phenotypic character is studied.  Among different characters of test individuals, only one of the dominant characters is considered. In a monohybrid test cross, a 1:1 phenotypic ratio is obtained if the test individual is heterozygous.

Let’s consider an example where a red flower (dominant) bearing plant is crossed with a yellow flower (recessive) plant. Here, a red flower may be either homozygous (RR) or heterozygous (Rr), but the yellow one being recessive is always homozygous (rr).

To know the genotype of the red flower test cross is done and the following results are obtained:

1. If the red flower is homozygous dominant (RR)

Phenotypic ratio : Red : Yellow = 1 : 0

Here all the offspring are phenotypically red. Hence, the test concludes that the test flower was homozygous red (RR).

2. If the red flower is heterozygous dominant (Rr)

Phenotypic ratio : Red : Yellow = 1 : 1

Here half of the offspring are phenotypically red and half are phenotypically yellow. Hence, the test concludes that the test flower was heterozygous red (Rr).

B. Dihybrid Test Cross (Two Gene Test Cross)

Also called ‘two-gene test cross’, is a type of testcross where two types of genes or phenotypic characters are studied.  Among different characters of test individuals, only two of the dominant characters are considered. A test individual with two selected dominant phenotypic characters is crossed with double recessive parents and the phenotypic characters of F1 generations are studied.  In a dihybrid test cross, a 1:1:1:1 phenotypic ratio is obtained if the test individual is heterozygous.

Let’s consider an example where a red flower tall plant (dominant) bearing plant is crossed with a yellow flower dwarf plant (recessive) plant. Here, a red flower tall plant may be either homozygous (RRTT) or heterozygous (RrTt), but the yellow flower dwarf plant is always homozygous (rrtt).

To know the genotype of the individual with dominant characters test cross is done and the following results are obtained:

1. If the test plant is heterozygous dominant (RrTt)

 rtrt
RT
Rt
rT
rt

Phenotypic ratio : Red/Tall : Red/Dwarf : Yellow/Tall : Yellow/Dwarf = 1 : 1 : 1 : 1

Here 25% of offspring are red and tall, 25% of offspring are red and dwarf, 25% of offspring are yellow and tall, and the rest 25% of offspring are yellow and dwarf.  Hence, the test concludes that the test individual was a heterozygous red flower tall plant (RrTt).

2. If the test plant is homozygous dominant (RRTT)

 rtrt
RT
RT
RT
RT

Phenotypic ratio : Red/Tall : Red/Dwarf : Yellow/Tall : Yellow/Dwarf = 1 : 0 : 0 : 0

Here all the offspring are red flower tall plants. Hence, the test concludes that the test individual was a homozygous red flower tall plant (RRTT).

C. Trihybrid Test Cross (Triple Gene Test Cross)

Also called ‘triple gene test cross’, is a type of testcross where three types of genes or phenotypic characters are studied.  Among different characters of test individuals, only three of the dominant characters are considered. A test individual with three selected dominant phenotypic characters is crossed with a triple recessive parent and the phenotypic characters of F1 generations are studied. In a trihybrid test cross, a 1:1:1:1:1:1:1:1 phenotypic ratio is obtained if the test individual is heterozygous.

Let’s consider an example where a red flower tall plant with normal leaves (dominant) bearing plant is crossed with a yellow flower dwarf plant with wrinkled leaves (recessive) plant. Here, a red flower tall plant with normal leaves may be either homozygous (RRTTNN) or heterozygous (RrTtNn), but a yellow flower dwarf plant with wrinkled leaves is always homozygous (rrttnn).

1. If the plant is heterozygous dominant (RrTtNn)

 

Phenotypic ratio : red/tall/normal : red/tall/wrinkled : red/dwarf/normal : red/dwarf/wrinkled : yellow/tall/normal : yellow/tall/wrinkled : yellow/dwarf/normal : yellow/dwarf/wrinkled =  1 : 1 : 1: 1 : 1 : 1 : 1 : 1

Here, 12.5% are red flower tall plant with normal leaves, 12.5% are red flower tall plant wrinkled leaves, 12.5% are red flower dwarf with normal leaves, 12.5% are red flower dwarf with wrinkled leaves, 12.5% are yellow flower tall with normal leaves, 12.5% are yellow flower tall with wrinkled leaves, 12.5% are yellow flower dwarf with wrinkled leave, and rest 12.5% are yellow flower dwarf with wrinkled leaves. The result concludes that the test individual was heterozygous dominant (RrTtNn).

2. If the plant is homozygous dominant (RRTTNN)

 

Phenotypic ratio : red/tall/normal : red/tall/wrinkled : red/dwarf/normal : red/dwarf/wrinkled : yellow/tall/normal : yellow/tall/wrinkled : yellow/dwarf/normal : yellow/dwarf/wrinkled =  1 : 0 : 0: 0 : 0 : 0 : 0 : 0

Here, all the offspring are red flower tall plants with normal leaves. The result concludes that the test individual was homozygous dominant (RRTTNN).

Applications of Test Cross

  • To determine the genotype of a dominant individual (F1 generation as well as a dominant parent)
  • To know the types and numbers of gametes formed
  • To separate pure and hybrid dominant breed

Limitations of Test Cross

  • Requires a large number of offspring for confirmation
  • Applicable only in case of Mendelian genetic inheritance
  • Difficulty to study a large number of characters and genes at a single cross
  • It is not suitable in the case of species with a very long generation time
  • Agarwal, P. V. | V. (2004). Cell Biology, Genetics, Molecular Biology, Evolution and Ecology: Evoloution and Ecology. S. Chand Publishing.
  • Test Cross – Definition and Examples | Biology Dictionary
  • Zhu, C., Zhang, R. Efficiency of triple test cross for detecting epistasis with marker information. Heredity 98, 401–410 (2007). https://doi.org/10.1038/sj.hdy.6800956
  • Testcross – definition of testcross by The Free Dictionary
  • Testcross Definition & Meaning – Merriam-Webster
  • What Is Test Cross? – Explore More at BYJU’S NEET (byjus.com)
  • Test Cross | BioNinja
  • What is a ‘test cross’? Explain significance of a test cross. (toppr.com)
  • What is a Test Cross: Why is it used (Biology) | SchoolWorkHelper
  • Test Cross – Notes – Biology | Mrs. McComas (weebly.com)
  • Test Crosses | Learn Science at Scitable (nature.com)
  • Monohybrid, Dihybrid, Cross, Backcross And Testcross (learninsta.com)

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Test Cross: An Introduction

A test cross is a cross between a person with an unknown genotype and another person with a homozygous recessive genotype. A test cross determines or discloses the genotype of the original person. A test cross can assist in determining if a dominant phenotype is homozygous or heterozygous for a certain trait.

A test cross is a genetic technique discovered by Gregor Mendel that entails mating an individual with all phenotypically recessive individuals, to ascertain the zygosity of the former by evaluating the proportions of offspring phenotypes. Zygosity can be homozygous or heterozygous. Heterozygous individuals have one dominant and one recessive allele .

Individuals with homozygous dominant alleles have two dominant alleles, whereas individuals with homozygous recessive alleles have two recessive alleles. The alleles inherited from the parents define the genotype of an offspring for each of its genes.

The allele combination is the product of the maternal and paternal chromosomes provided by each gamete during the fertilisation of that offspring. During meiosis in gametes, homologous chromosomes undergo genetic recombination and randomly separate into haploid daughter cells , each with a unique combination of maternally and paternally coded genes. Dominant alleles will overpower recessive allele expression.

The genotypic ratios may be derived using mathematical probability, but the genotypic composition cannot be determined merely by looking at the phenotype of a dominant feature. It is impossible to determine whether a tall plant from F1 or F2 has TT or Tt composition.

As a result, Mendel crossed a tall plant from F2 with a dwarf plant to identify the genotype of a tall plant at F2. It is known as a test cross. Instead of self-pollination, a dominant phenotypic organism is mated with a recessive parent in a normal test cross. The offspring of such a hybrid is simply analysed to predict the genotype of the test organism.

Test Cross Example

Let’s assume that you were handed a tall pea plant with no knowledge of its parentage. Since tallness is a dominant feature in peas, your plant may be homozygous (TT) or heterozygous (Tt), but you'd have no idea. In this case, a test cross can be used to establish its genotype.

If the plant were homozygous (TT), a test cross would produce all tall progeny (TT 🡪 tt: all Tt); if the plant were heterozygous (Tt), the test cross would produce half tall progeny and half short progeny (Tt 🡪 tt: Tt and tt).

Any recessive allele in the unknown genotype is expressed in the progeny of a test cross because it is linked with a recessive allele from the homozygous recessive parent.

Test Cross

What is Homozygous and Heterozygous?

Mendel hypothesised that the allelic pair of genes for height in a pure breeding tall or dwarf pea variety are identical. TT and tt, Bateson and Saunders referred to this situation as “homozygous.” A hybrid is an individual who has two distinct alleles (Tt). This condition was termed heterozygous by Bateson and Saunders.

Individual phenotype, DD and Dd are tall, but dd is a dwarf. When both alleles are the same (DD or dd), the individual is called a homozygote; when the alleles are different (Dd), the words heterozygous and heterozygote are used.

Homozygous Recessive

The organism with an unknown genotype that expresses the dominant phenotype is crossed with a known homozygous recessive individual.

Cross Genetics

Monohybrid Cross

A monohybrid cross is a cross between two individuals who have homozygous genotypes for the opposing phenotype for a certain genetic characteristic. Geneticists utilise monohybrid crosses to study how homozygous children express heterozygous genes acquired from their parents.

Dihybrid Cross

A dihybrid cross is a cross between two distinct genes whose observable features differ. It is the result of a cross between two heterozygous people, for two separate features.

Two lines are crossed to produce a hybrid in a back cross. The offspring are then selected and crossed with one of the parents. Back crosses are extremely beneficial in plant breeding because they allow breeders to hybridise a high-yielding variety with another variety to introduce the desired feature, then back cross to ensure the progeny have the same desirable qualities as the high-yielding variety.

Back Cross

This article covers the test cross, who discovered the test cross and various examples of it. It also stated the difference between homozygous and heterozygous . We have seen a homozygous example and a heterozygous example, and understood the difference between dominant and recessive. Also, how heterozygous recessive can’t show a trait but can become the carrier.

FAQs on Test Cross

1. What is the significance of the test cross?

The significance of the test cross:

Very important in identifying an organism's genetic composition.

Simpler and faster way of obtaining desirable characteristics in homozygous individuals.

Used to establish linkage relationships between genes.

Extremely beneficial to breeders and geneticists.

It aids in determining an organism's genetic make-up.

2. Explain the differences between monohybrid and dihybrid crosses.

A monohybrid cross occurs when two individuals have homozygous genotypes for the opposite phenotype for a certain genetic trait. A dihybrid cross is a cross between two distinct genes whose observable features differ. It is the result of a cross between two people who are heterozygous for two separate features.

The number of characteristics investigated in the offspring distinguishes a monohybrid cross from a dihybrid cross. The inheritance of a single gene is anticipated in a monohybrid cross since the parents are homozygous, however in a dihybrid cross, the parents vary in two separate features.

3. What are the disadvantages of test cross?

The disadvantages of test cross are:

It is ineffective for quantitative traits.

It is more limited in recessive traits.

In reality, portions of the genome from non-recurrent parents are frequently present and can be associated with undesirable features.

Limited recombination may keep thousands of 'foreign' genes within the elite cultivar over extremely broad crosses.

Many backcrosses are needed to create a new cultivar, which might take years.

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Test Crosses

assignment on test cross

Single-Gene Test Crosses

       

Two-Gene Test Crosses

Allele Allele Allele Allele 1 0 0 0 0.5 0.5 0 0 0.5 0 0.5 0 0.25 0.25 0.25 0.25 0.5 (1) (0.5) 0.5 (1) (0.5)

References and Recommended Reading

Mendel, G. Versuche über Plflanzen-hybriden. Verhandlungen des naturforschenden Ver-eines in Brünn, Bd. IV für das Jahr 1865, Abhand-lungen, 3-47 (1866) (Bateson translation)

Pierce, B. Genetics: A Conceptual Approach , 2nd ed. (New York, W. H. Freeman, 2006)

Sadava, D., et al . Life: The Science of Biology , 8th ed. (New York, W. H. Freeman/Sinaeur Associates, 2008)

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Testcross (Backcross; concepts of parental, F1, and F2 generations)

A test cross is a way to determine whether an organism that expressed a dominant trait was homozygous or heterozygous ; backcross is the mating between parent and offspring to preserve the parental genotype ; P represents parent, F1 (filial 1) represents the children of the parent and F2 represents the children of the F1.

In genetics, dominant alleles are assigned capital letters (e.g., AA), and recessive alleles are assigned lowercase letters (aa). If both copies of the allele are the same, that individual is said to be homozygous. If they are different, the individual is heterozygous (Aa, aA). The parent or P generation refers to the individuals being crossed. The offspring are the filial or F generation; F₁  or the first filial represents the children of the parents while the F₂ represents children of the F1 or grandchildren of the parents.

Image result for heterozygous

Homozygous and Heterozygous Genotypes . Two dominant alleles (BB) or two recessive alleles (bb) are homozygous. One dominant allele and one recessive allele (Bb or bB) are heterozygous.

A  test cross  can be performed to determine whether an organism expressing a dominant trait is homozygous or heterozygous. Meaning, this is a way to tell what hidden genes are carried, but not shown. In a test cross, if you want to find out if the dominant trait is homozygous or heterozygous, it must be crossed with the homozygous recessive (bb). If the offspring is Bb, half the offspring will express the recessive trait. If it is BB, all offspring will express the dominant trait, and none will express the recessive trait. For instance, if the parent has blue eyes, and one of her children has brown eyes, then the parent is a heterozygous dominant. 

Because a test cross is used to determine the genotype of the parent based on the phenotypes of its offspring, test crosses are sometimes called backcrosses.  The backcross  is mating between the offspring and the parent to preserve the parental genotype.

Practice Questions

MCAT Official Prep (AAMC)

Biology Question Pack, Vol 2. Question 82

Sample Test B/B Section Passage 7 Question 38

Section Bank B/B Section Question 30

Practice Exam 4 B/B Section Question 58

• A test cross is a way to determine whether an organism that expressed a dominant trait was a heterozygote or a homozygote.

• In a test cross, the dominant trait must be crossed with the homozygous recessive to know whether it is homozygous or heterozygous it. If the offspring is recessive, half the offspring will express the recessive trait. If it is dominant, all offspring will express the dominant trait, and none will express the recessive trait.

• The parent or P generation refers to the individuals being crossed; the offspring are the filial or F generation.

• F₁ or the first filial represents the children of the parents; F₂ represents children of the F₁ or grandchildren of the parents.

• The backcross  is mating between the offspring and the parent to preserve the parental genotype.

Testcross : a cross between an organism showing a dominant trait and an organism showing a recessive trait to determine whether the former organism is homozygous or heterozygous for that trait

Filial : offspring, daughter or son

Phenotype : the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment

Genotype : the part of the genetic makeup of a cell or an individual which determines one of its characteristics (phenotype)

Dominant : a relationship between alleles of a gene, in which one allele masks the expression (phenotype) of another allele at the same locus

Homozygous : of an organism in which both copies of a given gene have the same allele

Heterozygous : of an organism which has two different alleles of a given gene

Recessive : an allele that can be covered up by a dominant trait, represented by a lower case letter

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2.5 The Dihybrid Test Cross

While the cross of an F 1 x F 1 gives a ratio of 9:3:3:1, there is a better, easier cross to test for independent assortment: the dihybrid test cross. In a dihybrid test cross, independent assortment is seen as a ratio of 1:1:1:1, which is easier to score than the 9:3:3:1 ratio. This test cross will also be easier to use when testing for linkage.

Like in monohybrid crosses ( Chapter 1 ), you can do test crosses with dihybrids to determine the genotype of an individual with dominant phenotypes, to see if they are heterozygous or homozygous dominant. This type of cross is set up in the same fashion; an individual with an unknown genotype in two loci is crossed to an individual that is homozygous recessive for both loci.

Take a look at the video, Two-Gene Test Cross Explained , by Nicole Lantz (2020) on YouTube, for some worked examples.

Punnett squares should be done ahead of the crosses, so you know what to expect for any of the possible outcomes. Using the example from the rest of this chapter, you cross a double homozygous recessive pea plant (r/r ; y/y. green and wrinkled) to an unknown individual that has two dominant phenotypes (R/_ ; Y/_. yellow and round). There are four possible genotypes the unknown individual could be: R/R ; Y/Y or R/R ; Y/y or R/r ; Y/Y or R/r; Y/y. The Punnett squares for the first two are shown in Figure 2.5.1 . Notice on the left, you only get the dominant phenotype for both, so you know both genes in the unknown are homozygous dominant. On the right, you get only the dominant phenotype for round peas — but you get 50% yellow and 50% green peas, showing that the unknown is homozygous for round, but heterozygous for colour of the peas. Figure 2.5.2  is blank for you to fill in the other two gamete and genotype possibilities.

Media Attributions

  • Figure 2.5.1 , Original by L.Canham (2017), CC BY-NC 3.0
  • Figure 2.5.2 , Original by L.Canham (2017), CC BY-NC 3.0

Canham, L. (2017). Figures: 7. Punnett square for a test cross; 8. Blank Punnett squares to fill in the other two possibilities of the test cross [digital images]. In Locke, J., Harrington, M., Canham, L. and Min Ku Kang (Eds.),  Open Genetics Lectures, Fall 2017 (Chapter 17, p. 6-7). Dataverse/ BCcampus. http://solr.bccampus.ca:8001/bcc/file/7a7b00f9-fb56-4c49-81a9-cfa3ad80e6d8/1/OpenGeneticsLectures_Fall2017.pdf

Nicole Lantz. (2020, May 5). Two-gene test cross explained [Video file]. YouTube. https://youtu.be/GM0by2axiLM

Long Descriptions

  • Figure 2.5.1 Two Punnett squares: The first is a testcross between a dihybrid homozygous dominant organism (RRYY) and the tester, which is a dihybrid homozygous recessive organism (rryy). The offspring and their genotypes in this test cross are shown, with all possessing the heterozygous condition for both traits (RrYy). The second is a testcross between a dihybrid heterozygous organism (RrYy) and the tester, which is a dihybrid homozygous recessive organism (rryy). The offspring and their genotypes in this test cross are shown, with half possessing the heterozygous condition for both traits (RrYy) and the other half expressing the genotype Rryy. [Back to Figure 2.5.1 ]
  • Figure 2.5.2 A blank Punnett square can be used for practice, and to fill in the other two gamete and genotype possibilities for the question in the text directly preceding this figure. [Back to Figure 2.5.2 ]

Introduction to Genetics Copyright © 2023 by Natasha Ramroop Singh, Thompson Rivers University is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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Biology (Year 12) - Genetics

Ben Whitten

A test cross is a technique used by geneticists in which an individual whose genotype is unknown for a dominant phenotype (it could be homozygous dominant or heterozygous dominant ) is crossed with an individual that is homozygous recessive at the locus in question. The ratio of phenotypes in the offspring reveals the unknown genotype. Drosophila melanogaster is the scientific name for the fruit fly and is an excellent example of where test crosses are used as they have a large number of variants. The long-winged condition is dominant (V) to the vestigial, recessive (non-useful) wing (v). If a pure-breeding long-winged fly (VV) is mated with a vestigial-winged fly (vv), then the F1 generation (first filial) will all be heterozygous (Vv) and have long wings. However, how can it be decided whether a given F2 long-winged fly will be homozygous dominant (VV) or heterozygous (Vv)? This is determined by crossing the unknown genotype with a vestigial-winged fly. As a vestigial-winged fly must be homozygous recessive (vv), if the long-winged fly whose genotype is unknown is VV, crossing with the homozygous recessive fly will produce all long-winged flies. However, if the unknown fly is heterozygous (Vv), there will be a mix of long and vestigial-winged flies in equal numbers (approximately).

One bed, two blankets: We put the Scandinavian sleep method to the test

If you sleep with a cover hog, this might be for you.

assignment on test cross

There are plenty of Scandinavian exports worth embracing, including saunas , Lego , Dansk tableware , the Billy bookcase , Kransekake , Marimekko . So when the Scandinavian sleep method started popping up everywhere on social media , I took note.

The idea: Two people share a bed but use separate covers. The promise: a better night’s sleep. The bedding arrangement is popular in other European countries as well; on a trip to Paris a couple of years ago, our hotel room bed was outfitted with two sets of blankets and top sheets.

But does the method work? And how do you make a bed with two blankets? We put it to the test. We gave five couples two twin-size down alternative comforters each and asked them to try the method for a week. Here’s what they had to say.

Typical sleeping arrangement: Queen-size bed with a flat sheet, blanket and comforter.

Pain points: Tester 1’s husband accuses her of being a chronic sheet stealer, but she thinks the main issue is that they operate at different temperatures: “I am a nuclear furnace when I sleep, while my husband is a block of ice,” she says. Regardless, it seems like someone is always getting shortchanged on covers, or someone is tossing and turning.

How they carried out the test: They used the separate comforters, no flat sheet or blankets.

The experience: She likes to throw her foot or leg out from under the covers when she gets too hot, and the separate covers allowed her to do this on both sides, instead of just one. Another bonus: Lounging in bed on weekends was better with the extra covers. “It was absolutely luxuriant to take over the whole bed and both comforters and do the crossword puzzle,” she says. Her husband liked that he could roll over and move around in bed without affecting his wife.

The bed-making problem: They don’t typically make their bed, so this wasn’t an issue. “No shade on anyone who is put together enough in the morning to arrange their bedding, but we usually leave it in a chaotic state, and tend to reassemble the tangle of sheets into something more coherent as we’re going to bed, not when we wake up,” she says.

The verdict: The arrangement worked well for them, and they may implement it in the future. “The only hesitation is that we have so much bedding, buying more almost becomes a storage problem at this point,” she says. “But I think we slept better and more comfortably, so if I see twin comforters on sale anytime soon, there’s a good chance we will make the switch.”

Typical sleeping arrangement: Queen-size bed with a top sheet and a duvet.

Pain points: Tester 2 and her husband often go to bed at different times, and many nights one of them has to get up to tend to their toddler, which can be disruptive. There are also issues with sharing covers, she says: “One of us (a.k.a. me) is allegedly a cover hog, which means the other of us sleeps in a defensive crouch with respect to the shared covers as a way to maintain some blanket.”

How they carried out the test: They started with the two twin-size down alternative duvets provided, but her husband didn’t like the texture, so he swapped his out for a twin-size quilt they had. And she realized she preferred a bigger blanket, so she swapped in a queen-size quilt. They kept their queen-size flat sheet.

The experience: The test went well for this couple. Even the difference of opinions on the blankets ended up working in their favor. “The idea that we could each seek out a blanket with our preferred texture and warmth level was an improvement on sharing one quilt,” she says. “It was great to each have our own quilt and made for more restful sleeping.”

The bed-making problem: They don’t make the bed daily but like to do it when time allows. Settling on one twin quilt for him and a queen-size quilt for her helped here. During the day, they made the bed with the queen-size cover and folded the twin cover across the bottom of the bed.

The verdict: They said the arrangement was a big improvement on their previous blanket-sharing situation and plan to continue to use it.

Typical sleeping arrangement: Queen-size bed with a top sheet and comforter.

Pain points: Tester 3 says her husband is an occasional cover-stealer, and she’s a light sleeper who wakes easily if he is tossing and turning.

How they carried out the test: They used the twin comforters and skipped the flat sheet.

The experience: Her husband tossed and turned a good bit one night, and got up to use the bathroom several times on another night, but it didn’t disturb her. She says, though, that she’s so used to his restlessness that she might not have been disturbed even while sharing covers. She liked being able to stick her leg out from under the covers on either side. But there were also drawbacks, including getting overheated. “I think during the night, the excess parts of our blankets would overlap on one person or the other,” she says.

The bed-making problem: They folded the twin comforters lengthwise and placed them side by side to give the bed a neat appearance.

The verdict: They plan to keep their original bedding configuration. “I don’t think we saw enough of a positive impact to switch to two blankets,” she says. She also likes having a neatly made bed, which was another strike against the Scandinavian method.

Typical sleeping arrangement: King-size bed with a flat sheet, blanket and duvet.

Pain points: Tester 4 likes to have covers tucked snugly around her, while her husband struggles to keep his side tucked. Sometimes that leads to uneven distribution of blankets. She maintains that because his covers are untucked, they bunch up at the bottom, creating the impression that she’s stolen them when, in fact, she has not. He admits this possibility: “I think I kick covers off and then overcompensate when trying to recover (ha),” he says. “Then the groggy tug-of-war begins.”

How they carried out the test: They used the two twin duvets provided and dragged out old twin-size top sheets from when their kids were little, giving them completely separate covers.

The experience: The test took cover-stealing out of the equation, and she reports that she was less aware of when her husband got in and out of bed (he goes to bed later — and gets up earlier — than she does). “Something has to go pretty wrong for you to end up with the other person’s covers,” her husband says. “I don’t really see a downside to it. It’s the happy medium between the freedom of separate beds and the traditional way that just doesn’t work for many people.” It didn’t solve his issues with keeping his covers in order; sometimes he woke up with just the duvet and couldn’t find the top sheet. She liked the fact that he couldn’t blame her for this problem anymore. Overall, it improved their quality of sleep.

The bed-making problem: They typically don’t make their bed, so this wasn’t an issue.

The verdict: They have returned to their usual sleeping arrangements for now, but may switch at some point in the future if they find bedding they like.

Typical sleeping arrangement: A queen bed with a flat sheet, blanket and comforter.

Pain points: Tester 5 says she and her partner’s covers come untucked at times, but overall, they don’t have issues with sharing. She sleeps “warm,” so prefers a cool room with a fan pointing at her, and often wakes up under just the sheet.

How they carried out the test: They started with just the separate comforters but missed having a top sheet, so after a week, they brought back a shared queen-size sheet.

The experience: While they slept well during the test, they didn’t notice much of a difference between sharing a comforter or having separate ones. “We already have a comforter we like enough, and both of us prefer to have a flat sheet between the comforter and ourselves,” she says. After a few nights, they added a sheet and blanket for her partner, who sleeps cooler. And after a week, they brought back the queen-size top sheet. Overall, they didn’t notice much of a difference sleeping with two duvets, possibly because they don’t struggle with sharing covers.

The bed-making problem: It’s easier to make the bed with fewer covers, she says, but it definitely looked less tidy. When her parents came to visit, they tossed their regular comforter over the bed for a neater appearance.

The verdict: They felt pretty neutral about the test and have gone back to their regular sleeping arrangement. “I think this is fine when we travel … but isn’t a huge benefit at home,” she says.

assignment on test cross

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What Is Test Cross?

Test cross: a test cross is a cross between an individual with an unknown genotype with a homozygous recessive genotype. the test cross research was initially used by gregor johann mendel. it is used to know whether the trait which is dominant is heterozygous or homozygous..

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Explain what is test cross?

What is test cross and its significance?

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  • Open access
  • Published: 26 June 2024

Comparative accuracy of ChatGPT-4, Microsoft Copilot and Google Gemini in the Italian entrance test for healthcare sciences degrees: a cross-sectional study

  • Giacomo Rossettini   ORCID: orcid.org/0000-0002-1623-7681 1 , 2 ,
  • Lia Rodeghiero 3 ,
  • Federica Corradi 4 ,
  • Chad Cook   ORCID: orcid.org/0000-0001-8622-8361 5 , 6 , 7 ,
  • Paolo Pillastrini   ORCID: orcid.org/0000-0002-8396-2250 8 , 9 ,
  • Andrea Turolla   ORCID: orcid.org/0000-0002-1609-8060 8 , 9 ,
  • Greta Castellini   ORCID: orcid.org/0000-0002-3345-8187 10 ,
  • Stefania Chiappinotto   ORCID: orcid.org/0000-0003-4829-1831 11 ,
  • Silvia Gianola   ORCID: orcid.org/0000-0003-3770-0011 10   na1 &
  • Alvisa Palese   ORCID: orcid.org/0000-0002-3508-844X 11   na1  

BMC Medical Education volume  24 , Article number:  694 ( 2024 ) Cite this article

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Artificial intelligence (AI) chatbots are emerging educational tools for students in healthcare science. However, assessing their accuracy is essential prior to adoption in educational settings. This study aimed to assess the accuracy of predicting the correct answers from three AI chatbots (ChatGPT-4, Microsoft Copilot and Google Gemini) in the Italian entrance standardized examination test of healthcare science degrees (CINECA test). Secondarily, we assessed the narrative coherence of the AI chatbots’ responses (i.e., text output) based on three qualitative metrics: the logical rationale behind the chosen answer, the presence of information internal to the question, and presence of information external to the question.

An observational cross-sectional design was performed in September of 2023. Accuracy of the three chatbots was evaluated for the CINECA test, where questions were formatted using a multiple-choice structure with a single best answer. The outcome is binary (correct or incorrect). Chi-squared test and a post hoc analysis with Bonferroni correction assessed differences among chatbots performance in accuracy. A p -value of < 0.05 was considered statistically significant. A sensitivity analysis was performed, excluding answers that were not applicable (e.g., images). Narrative coherence was analyzed by absolute and relative frequencies of correct answers and errors.

Overall, of the 820 CINECA multiple-choice questions inputted into all chatbots, 20 questions were not imported in ChatGPT-4 ( n  = 808) and Google Gemini ( n  = 808) due to technical limitations. We found statistically significant differences in the ChatGPT-4 vs Google Gemini and Microsoft Copilot vs Google Gemini comparisons ( p -value < 0.001). The narrative coherence of AI chatbots revealed “Logical reasoning” as the prevalent correct answer ( n  = 622, 81.5%) and “Logical error” as the prevalent incorrect answer ( n  = 40, 88.9%).

Conclusions

Our main findings reveal that: (A) AI chatbots performed well; (B) ChatGPT-4 and Microsoft Copilot performed better than Google Gemini; and (C) their narrative coherence is primarily logical. Although AI chatbots showed promising accuracy in predicting the correct answer in the Italian entrance university standardized examination test, we encourage candidates to cautiously incorporate this new technology to supplement their learning rather than a primary resource.

Trial registration

Not required.

Peer Review reports

Being enrolled in a healthcare science degree in Italy requires a university examination, which is a highly competitive and selective process that demands intensive preparation worldwide [ 1 ]. Conventional preparation methods involve attending classes, studying textbooks, and completing practical exercises [ 2 ]. However, with the emergence of artificial intelligence (AI), digital tools like AI chatbots to assist in exam preparation are becoming more prevalent, presenting novel opportunities for candidates [ 2 ].

AI chatbots such as ChatGPT, Microsoft Bing, and Google Bard are advanced language models that can produce responses similar to humans through a user-friendly interface [ 3 ]. These chatbots are trained using vast amounts of data and deep learning algorithms, which enable them to generate coherent responses and predict text by identifying the relationships between words [ 3 ]. Since their introduction, AI chatbots have gained considerable attention and sparked discussions in medical and health science education and clinical practice [ 4 , 5 , 6 , 7 ]. AI chatbots can provide simulations with digital patients, personalized feedback, and help eliminate language barriers; they also present biases, ethical and legal concerns, and content quality issues [ 8 , 9 ]. As such, the scientific community recommends evaluating the AI chatbot’s accuracy of predicting the correct answer (e.g., passing examination tests) to inform students and academics of their value [ 10 , 11 ].

Several studies have assessed the accuracy of AI chatbots to pass medical education tests and exams. A recent meta-analysis found that ChatGPT-3.5 correctly answered most multiple-choice questions across various medical educational fields [ 12 ]. Further research has shown that newer versions of AI chatbots, such as ChatGPT-4, have surpassed their predecessors in passing Specialty Certificate Examinations in dermatology [ 13 , 14 ], neurology [ 15 ], ophthalmology [ 16 ], rheumatology [ 17 ], general medicine [ 18 , 19 , 20 , 21 ], and nursing [ 22 ]. Others have reported mixed results when comparing the accuracy of multiple AI chatbots (e.g., ChatGPT-4 vs Microsoft Bing, ChatGPT-4 vs Google Bard) in several medical examinations tests [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. Recently, two studies observed the superiority of ChatGPT-3.5 over Microsoft Copilot and Google Bard in hematology [ 30 ] and physiology [ 31 ] case solving. Recent work has also observed that ChatGPT-4 outperformed other AI Chatbots in clinical dentistry-related questions [ 32 ], whereas another revealed that ChatGPT-4 and Microsoft Bing outperformed Google Bard and Claude in the Peruvian National Medical Licensing Examination [ 33 ].

These findings suggest a potential hierarchy in accuracy of AI chatbots, although continued study in medical education is certainly warranted [ 3 ]. Further, current studies are limited by predominantly investigating: (A) a single AI chatbot rather than multiple ones; (B) examination tests for students and professionals already in training rather than newcomers to the university; and (C) examination tests for medical specialities rather than for healthcare science (e.g., rehabilitation and nursing). Only two studies [ 34 , 35 ] have attempted to address these limitations, identifying ChatGPT-3.5 as a promising, supplementary tool to pass several standardised admission tests in universities in the UK [ 34 ] and in France [ 35 ]. To our knowledge, no study has been performed on admission tests for admissions to a healthcare science degree program. Healthcare Science is a profession that includes over 40 areas of applied science that support the diagnosis, rehabilitation and treatment of several clinical conditions [ 36 ]. Moreover, the only studies conducted in Italy concerned ChatGPT's accuracy in passing the Italian Residency Admission National Exam for medical graduates [ 37 , 38 ] offering opportunities for further research setting.

Accordingly, to overcome existing knowledge gaps, this study aimed to assess the comparative accuracy of predicting the correct answer of three updated AI chatbots (ChatGPT-4, Microsoft Copilot and Google Gemini) in the Italian entrance university standardized examination test of healthcare science. The secondary aim was to assess the narrative coherence of the text responses offered by the AI chatbots. Narrative coherence was defined as the internally consistency and sensibility of the internal or external explanation provided by the chatbot.

Study design and ethics

We conducted an observational cross-sectional study following the Strengthening of Reporting of Observational Studies in Epidemiology (STROBE) high-quality reporting standards [ 39 ]. Because no human subjects were included, ethical approval was not required [ 40 ].

This study was developed by an Italian multidisciplinary group of healthcare science educators. The group included professors, lecturers, and educators actively involved in university education in different healthcare disciplines (e.g., rehabilitation, physiotherapy, speech therapy, nursing).

In Italy, the university’s process of accessing the healthcare professions is regulated by the laws according to short- and long-term workforce needs [ 41 ]. Consequently, the placements available for each degree are established in advance; to be enrolled in an academic year, candidates should take a standardized examination test occurring on the same day for all universities. This process, in most Italian universities, is annually managed by the CINECA (Consorzio Interuniversitario per il Calcolo Automatico dell'Italia Nord Orientale), a governmental organization composed of 70 Italian universities, 45 national public research centers, the Italian Ministry of University and Research, and the Italian Ministry of Education [ 42 ]. CINECA prepares the standardized test common to all healthcare disciplines (e.g., nursing and midwifery, rehabilitation, diagnostics and technical, and prevention) for entrance to University [ 43 ]. The test assesses basic knowledge useful as a prerequisite for their future education [ 44 ], in line with the expected knowledge possessed by candidates that encompass students at the end of secondary school, including those from high schools, technical, and professional institutes [ 45 ].

For this study, we adopted the official CINECA Tests from the past 13 years (2011–2023) obtained from freely available public repositories [ 46 , 47 ]. The CINECA Test provided 60–80 range of independent questions per year for a total of 820 multiple-choice questions considered for the analysis. Every question presents five multiple-choice options, with only one being the correct answer and the remaining four being incorrect [ 44 ]. According to the law, over the years, the CINECA test consisted of multiple-choice questions covering four areas: (1) logical reasoning and general culture, (2) biology, (3) chemistry, and (4) physics and mathematics. The accuracy of each AI chatbot was evaluated as the sum of the proportion of correct answers provided among all possible responses for each area and for the total test. In Additional file 1, we reported all the standardized examination tests used in the Italian language and an example of the question stem that was exactly replicated.

Variable and measurements

We assessed the accuracy of three AI chatbots in providing accurate responses for the Italian entrance university standardized examination test for healthcare disciplines. We utilized the latest versions of ChatGPT-4 (OpenAI Incorporated, Mission District, San Francisco, United States) [ 48 ], Microsoft Copilot (Microsoft Corporation, WA, US) [ 49 ] and Google Gemini (Alphabet Inc., CA, US) [ 50 ] that were updated in September 2023. We considered the following variables: (A) the accuracy of predicting the correct answer of the three AI chatbots in the CINECA Test and (B) the narrative coherence and errors of the three AI chatbots responses.

The accuracy of three AI chatbots was assessed by comparing their responses to the correct answers from the CINECA Test. AI Chatbots’ answers were entered into an Excel sheet and categorized as correct or incorrect. Ambiguous or multiple responses were marked as incorrect [ 51 ]. Since none of the three chatbots has integrated multimodal input at this point, questions containing imaging data were evaluated based solely on the text portion of the question stem. However, technical limitations can be present, and a sensitivity analysis was performed, excluding answers that were not applicable (e.g., images).

The narrative coherence and errors [ 52 ] of AI chatbot answers for each question were assessed using a standardized system for categorization [ 53 ]. Correct answers were classified as [ 53 ]: (A) “Logical reasoning”, if they clearly demonstrated the logic presented in the response; (B) “Internal information”, if they included information from the question itself; and (C) “External information”, if they referenced information external to the question.

On the other side, incorrect answers were categorized as [ 53 ]: (A) “Logical error”, when they correctly identify the relevant information but fail to convert it into an appropriate answer; (B) “Information error”, if AI chatbots fail to recognize a key piece of information, whether present in the question stem or through external information; and (C) “Statistical error”, for arithmetic mistakes. An example of categorisation is displayed in Additional file 2. Two authors (L.R., F.C.) independently analyzed the narrative coherence, with a third (G.R.) resolving uncertainties. Inter-rater agreement was measured using Cohen’s Kappa, according to the scale offered by Landis and Koch: < 0.00 “poor”, 0–0.20 “slight”; 0.21–0.40 “fair”, 0.41–0.60 “moderate”, 0.61–0.80 “substantial”, 0.81–1.00 “almost perfect” [ 54 ].

We used each multiple-choice question of the CINECA Test, formatted for proper structure and readability. Because prompt engineering significantly affects generative output, we standardized the input formats of the questions following the Prompt-Engineering-Guide [ 55 , 56 ]. First, we manually entered each question in a Word file, left one line of space and then inserted the five answer options one below the other on different lines. If the questions presented text-based answers, they were directly inputted into the 3 AI chatbots. If the questions were presented as images containing tables or mathematical formulae, they were faithfully rewritten for AI chatbot processing [ 57 ]. If the answers had images with graphs or drawings, they were imported only into Microsoft Copilot because ChatGPT-4 and Google Gemini only accept textual input in their current form and could not process and interpret the meaning of complex images, as present in the CINECA Test, at the time of our study [ 58 ].

On 26th of September 2023, the research group copied and pasted each question onto each of the 3 AI chatbots in the same order in which it was presented in the CINECA Test [ 59 ] and without translating it from the original Italian language to English because the AIs are language-enabled [ 60 ]. To avoid learning bias and that the AI chatbots could learn or be influenced by conversations that existed before the start of the study, we: (A) created and used a new account [ 2 , 51 ], (B) always asked each question only once [ 61 , 62 ], (C) did not provide positive or negative feedback on the answer given [ 60 ], and (D) deleted conversations with the AI chatbots before entering each new question into a new chat (with no previous conversations). We presented an example of a question and answer in Additional file 3.

Statistical analyses

Categorical variables are presented as the absolute frequency with percent and continuous variables as mean with confidence interval (CI, 95%) or median with interquartile range (IQR). The answers were collected as binomial outcomes for each AI chatbot respect to the reference (CINECA Tests). A chi-square test was used to ascertain whether the CINECA Test percentage of correct answers differed among the three AI chatbots according to different taxonomic subcategories (logical reasoning and general culture, biology, chemistry, and physics and mathematics). A sensitivity analysis was performed, excluding answers that were not applicable (e.g., if the answers had images with graphs or drawings). A p -value of < 0.05 was considered significant. Since we are comparing three groups/chatbots, Bonferroni adjustment, Familywise adjustment for multiple measures, for multiple comparisons was applied. Regarding narrative coherence and errors, we calculated the overall correct answers as the relative proportion of correct answers provided among the overall test answers of each AI chatbot accuracy. A descriptive analysis of reasons for logical argumentation of correct answers and categorization of type error was reported by percentage in tables. Statistical analyses were performed with STATA/MP 16.1 software.

AI chatbots’ multiple-choice questions

From our original sample, we inputted all the multiple-choice questions in Microsoft Copilot ( n  = 820). Twelve multiple-choice questions were not imported in ChatGPT-4 ( n  = 808) and Google Gemini ( n  = 808) since they were images with graphs or drawings. The flowchart of the study is shown in Fig.  1 .

figure 1

The study flow chart

AI chatbots’ accuracy

Overall, we found a statistically significant difference in accuracy between the answers of the three chatbots ( p  < 0.001). The results of the Bonferroni adjustment, as a Familywise adjustment for multiple measures and tests between couples, are presented in Table  1 . We found a statistically significant difference in the ChatGPT-4 vs Google Gemini ( p  < 0.001) and Microsoft Copilot vs Google Gemini ( p  < 0.001) comparisons, which indicate a better ChatGPT-4 and Microsoft Copilot accuracy than Google Gemini (Table  1 ). A sensitivity analysis excluding answers that were not applicable (e.g., if the answers had images with graphs or drawings) showed similar results reported in Additional file 4.

AI chatbots’ narrative coherence: correct answers and errors

The Inter-rater agreement regarding AI chatbots’ narrative coherence was “almost perfect” ranging from 0.84–0.88 kappa for internal and logical answers (Additional file 5). The narrative coherence of AI chatbots is reported in Tables 2 and 3 . We excluded from these analyses all not applicable answers (ChatGPT-4: n  = 12, Microsoft Copilot: n  = 0, Google Gemini: n  = 12).

About the category of correct answer (Table  2 ), in ChatGPT-4 (tot = 763), the most frequent feature was “Logical reasoning” ( n  = 622, 81.5%) followed by “Internal information” ( n  = 141, 18.5%). In Microsoft Copilot (tot = 737), the main frequent feature was “Logical reasoning” ( n  = 405, 55%), followed by “External information” ( n  = 195, 26.4%) and “Internal information” ( n  = 137, 18.6%). In Google Gemini (tot = 574), the most frequent feature was “Logical reasoning” ( n  = 567, 98.8%), followed by a few cases of “Internal information” ( n  = 7, 1.2%).

With respect to category of errors (Table  3 ), in ChatGPT-4 (tot = 45), the main frequent reason was “Logical error” ( n  = 40, 88.9%), followed by a few cases of “Information error” ( n  = 4, 8.9%) and statistic ( n  = 1, 2.2%) errors. In Microsoft Copilot (tot = 83), the main frequent reason was “Logical error” ( n  = 66, 79.1%), followed by a few cases of “Information error” ( n  = 9, 11.1%) and “Statistical error” ( n  = 8, 9.8%) errors. In Google Gemini (tot = 234), the main frequent reason was “Logical error” ( n  = 233, 99.6%), followed by a few cases of “Information error” ( n  = 1, 0.4%).

Main findings

The main findings reveal that: (A) AI chatbots reported an overall high accuracy in predicting the correct answer; (B) ChatGPT-4 and Microsoft Copilot performed better than Google Gemini; and (C) considering the narrative coherence of AI chatbots, the most prevalent modality to present correct and incorrect answers were “Logical” (“Logical reasoning” and “Logical error”, respectively).

Comparing our study with existing literature poses a challenge due to the limited number of research that have examined the accuracy of multiple AI chatbots [ 30 , 31 , 32 , 33 ]. Our research shows that AI chatbots can accurately answer questions from the CINECA Test, regardless of the topics (logical reasoning and general culture, biology, chemistry, physics and mathematics). This differs from the fluctuating accuracy found in other studies [ 34 , 35 ]. Our findings support Torres-Zegarra et al.'s observations that the previous version of ChatGPT-4 and Microsoft Bing were superior to Google Bard [ 33 ], while other research groups did not confirm it [ 30 , 31 , 32 ]. This discrepancy may be due to differences in the tests used (e.g., medical specialties vs university entrance), the types of questions targeted at different stakeholders (e.g. professionals vs students), and the version of AI chatbots used (e.g., ChatGPT-3.5 vs 4).

The accuracy ranking of AI chatbots in our study might be due to differences in their neural network architecture. ChatGPT-4 and Microsoft Copilot AI use the GPT (Generative Pre-trained Transformer) architecture, while Google Gemini adopts LaMDA (Language Model for Dialogue Application) and later PaLM 2 (Pathways Language Model) in combination with web search [ 32 ]. The differences in the quality, variety, and quantity of data used for training, the optimization strategies adopted (e.g., fine-tuning), and the techniques applied to create the model could also account for the accuracy differences between AI chatbots [ 63 ]. Therefore, the variations mentioned above could lead to different responses to the same questions, affecting their overall accuracy.

In our study, the narrative coherence shows that AI chatbots mainly offer a broader perspective on the discussed topic using logical processes rather than just providing a simple answer [ 53 ]. This can be explained by the computational abilities of AI chatbots and their capacity to understand and analyze text by recognizing word connections and predicting future words in a sentence [ 63 ]. However, it is important to note that our findings are preliminary, and more research is needed to investigate how narrative coherence changes with advancements in AI chatbot technology and updates.

Implications and future perspective

Our study identifies two contrasting implications of using AI chatbots in education. The positive implication regards AI chatbots as a valuable resource, while the negative implication perceives them as a potential threat. First, our study sheds light on the potential role of AI chatbots as supportive tools to assist candidates in preparation for the Italian entrance university standardized examination test of healthcare science. They can complement the traditional learning methods such as textbooks or in-person courses [ 10 ]. AI chatbots can facilitate self-directed learning, provide explanations and insights on the topics studied, select and filter materials and can be personalized to meet the needs of individual students [ 10 ]. In addition to the knowledge components, these instruments contribute to developing competencies, as defined by the World Health Organization [ 64 ]. Virtual simulation scenarios could facilitate the development of targeted skills and attitudes where students have a virtual interlocutor with a dynamic and human-like approach driven by AI. However, we should highlight that they cannot replace the value of reflection and discussion with peers and teachers, which are crucial for developing meta-competencies of today's students and tomorrow's healthcare professionals [ 10 ]. Conversely, candidates must be protected from simply attempting to use these tools to answer questions while administering exams. Encouraging honesty by avoiding placing and using devices (e.g., mobile phones, tablets) in classrooms is important. Candidates must be encouraged to respond with their preparation and knowledge, given that they are mostly applying for professions where honesty and ethical principles are imperative.

Strengths and limitations

As a strength, we evaluated the comparative accuracy of three AI chatbots in the Italian health sciences university admissions test over the past 13 years on a large sample of questions, considering the narrative consistency of their responses. This enriches the international debate on this topic and provides valuable insights into the strengths and limitations of AI chatbots in the context of university education [ 2 , 3 , 8 , 9 , 11 ].

However, limitations exist and offer opportunities for future study. Firstly, we only used the CINECA Test, while other universities in Italy adopted different tests (e.g., CASPUR and SELECTA). Secondly, we studied three AI Chatbots without considering others presented in the market (e.g., Cloude, Perplexity) [ 31 ]. Thirdly, we adopted both paid (ChatGPT-4) and free (Microsoft Copilot and Google Gemini) versions of AI Chatbots. Although this choice may be a limitation, we aimed to use the most up-to-date and recent versions of the AI Chatbots available when the study was performed. Fourthly, although we inputted all queries into AI chatbots, we processed only some of them as only Microsoft Copilot was able to analyse complex images, as reported in the CINECA Tests, at the time of our study [ 65 , 66 , 67 ]. Fifthly, we inputted the test questions only once to simulate the test execution conditions in real educational contexts [ 32 ], although previous studies have prompted the test questions multiple times in AI chatbots to obtain better results [ 68 ]. However, an AI language model operates differently from regular, deterministic software. These models are probabilistic in nature, forming responses by estimating the probability of the next word according to statistical patterns in their training data [ 69 ]. Consequently, posing the same question twice may not always yield identical answers. Sixthly, we did not calculate the response time of the AI chatbots since this variable is affected by the speed of the internet connection and data traffic [ 51 ]. Seventhly, we assessed the accuracy of AI chatbots in a single country by prompting questions in Italian, which may limit the generalizability of our findings to other contexts and languages [ 70 , 71 ]. Finally, we did not compare the responses of AI chatbots with those of human students since there is no national ranking for admission in Italy, and each university draws up its ranking on its own.

AI chatbots have shown promising accuracy in quickly predicting correct answers, producing writing that is grammatically correct and coherent in a conversation for the Italian entrance university standardized examination test of healthcare science degrees. However, the study provides data regarding the overall performances of different AI Chatbots with regard to the standardized examinations provided in the last 13 years to all candidates willing to enter a healthcare science degree in Italy. Therefore, findings should be placed in the context of a research exercise and may support the current debate regarding the use of AI chatbots in the academic context. Further research is needed to explore the potential of AI chatbots in other educational contexts and to address their limitations as an innovative tool for education and test preparation.

Availability of data and materials

The datasets generated and/or analysed during the current study are available in the Open Science Framework (OSF) repository, https://osf.io/ue5wf/ .

Abbreviations

  • Artificial intelligence

Confidence interval

Consorzio Interuniversitario per il Calcolo Automatico dell'Italia Nord Orientale

Generative pre-trained transformer

Interquartile range

Language model for dialogue application

Pathways language model

Strengthening of Reporting of Observational Studies in Epidemiology

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Acknowledgements

The authors thanks Sanitätsbetrieb der Autonomen Provinz Bozen/Azienda Sanitaria della Provincia Autonoma di Bolzano for covering the open access publication costs.

The authors declare that they receive fundings from the Department of Innovation, Research, University and Museums of the Autonomous Province of Bozen/Bolzano for covering the open access publication costs of this study.

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Silvia Gianola and Alvisa Palese both authors have contributed equally.

Authors and Affiliations

School of Physiotherapy, University of Verona, Verona, Italy

Giacomo Rossettini

Department of Physiotherapy, Faculty of Sport Sciences, Universidad Europea de Madrid, Villaviciosa de Odón, 28670, Spain

Department of Rehabilitation, Hospital of Merano (SABES-ASDAA), Teaching Hospital of Paracelsus Medical University (PMU), Merano-Meran, Italy

Lia Rodeghiero

School of Speech Therapy, University of Verona, Verona, Italy

Federica Corradi

Department of Orthopaedics, Duke University, Durham, NC, USA

Duke Clinical Research Institute, Duke University, Durham, NC, USA

Department of Population Health Sciences, Duke University, Durham, NC, USA

Department of Biomedical and Neuromotor Sciences (DIBINEM), Alma Mater University of Bologna, Bologna, Italy

Paolo Pillastrini & Andrea Turolla

Unit of Occupational Medicine, IRCCS Azienda Ospedaliero-Universitaria Di Bologna, Bologna, Italy

Unit of Clinical Epidemiology, IRCCS Istituto Ortopedico Galeazzi, Milan, Italy

Greta Castellini & Silvia Gianola

Department of Medical Sciences, University of Udine, Udine, Italy

Stefania Chiappinotto & Alvisa Palese

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GR, SG, AP conceived and designed the research and wrote the first draft. LR, FC, managed the acquisition of data. SG, GC, SC, CC, PP, AT managed the analysis and interpretation of data. GR, SG, AP wrote the first draft. All authors read, revised, wrote and approved the final version of manuscript.

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A multidisciplinary group of healthcare science educators promoted and developed this study in Italy. The group consisted of professors, lecturers, and tutors actively involved in university education in different healthcare science disciplines (e.g., rehabilitation, physiotherapy, speech therapy, nursing).

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Rossettini, G., Rodeghiero, L., Corradi, F. et al. Comparative accuracy of ChatGPT-4, Microsoft Copilot and Google Gemini in the Italian entrance test for healthcare sciences degrees: a cross-sectional study. BMC Med Educ 24 , 694 (2024). https://doi.org/10.1186/s12909-024-05630-9

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Design and research of a strain elastic element with a double-layer cross floating beam for strain gauge wireless rotating dynamometers.

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1. Introduction

2. design and research of strain elastic element with double-layer cross floating beam, 2.1. structural design of strain gauge wireless rotating dynamometer, 2.2. structural design of the strain elastic element, 2.3. strain and deformation segmented rigid body model of double-layer cross floating beam, 2.3.1. strain and deformation analysis of double-layer cross floating beam under the action of f x, 2.3.2. strain and deformation analysis of double-layer cross floating beam under the action of f z, 2.4. comparison of fea solution and model solution for strain and deformation of double-layer cross floating beam, 2.5. size optimization of double-layer cross floating beam, 2.6. overall analysis of the strain elastic element, 3. strain gauge arrangement and testing, 3.1. strain gauge arrangement, 3.2. static calibration testing, 3.3. free modal testing, 3.4. cutting test, 4. conclusions.

  • This paper designed a compact strain elastic element with a double-layer cross floating beam. The maximum outer diameter is only 75 mm and the maximum thickness is 25 mm. The design of the double-layer cross floating beam allows the strain elastic element to improve the sensitivity and reduce the cross-sensitivity error while ensuring the overall stiffness;
  • Based on the proposed strain elastic element, a strain gauge wireless rotating dynamometer with compact size is designed. The overall diameter of the dynamometer is 170 mm and the axial size is 286 mm. In order to facilitate integration, a ring-shaped data acquisition and wireless transmission module PCB is designed;
  • The static model of the double-layer cross floating beam on the strain elastic element was established by the segmented rigid body method. The rationality of the model was verified by comparison with the finite element results. According to the obtained static model, the structural parameters of the double-layer cross floating beam were optimized using the sequential quadratic programming algorithm to maximize the sensitivity of the floating beam;
  • The strain elastic element was analyzed using finite element software, and the strain of the structure under simulation conditions was obtained, which provided a reference for subsequent calibration tests and circuit design;
  • Through static calibration tests, the sensitivities of the strain elastic element in the four directions of F X , F Y , F Z , and M Z are determined to be 3.3 mV/N, 2.7 mV/N, 1.6 mV/N, and 104.1 mV/Nm, respectively, and the maximum cross-sensitivity error does not exceed 1%. Through modal tests in the free state, the natural frequency of the strain elastic element is determined to be 2954 Hz. The results of cutting tests show that the strain elastic element can obtain the change in cutting force and the tool-passing frequency. The results show that the designed strain elastic element can be applied to the strain gauge wireless rotating dynamometer to measure four-component cutting forces under medium- and low-speed conditions.

Author Contributions

Data availability statement, conflicts of interest.

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Click here to enlarge figure

PropertiesValues
Young’s modulus (GPa) E206
Poisson’s ratio μ0.29
Shear modulus (GPa) G79.8
Yield strength (MPa) σ350
CaseSize (mm)Force (N)
acdehl
case181.51.57.56.756.58080
case281.527.56.56.5
case31011.57.56.759
case4811.57.56.757
CaseDesign Variables (mm)CaseDesign Variables (mm)
acd acd
18.51.11.62.5735 × 10 48.21.81.81.1519 × 10
29.51.91.70.9169 × 10 59.81.31.51.6964 × 10
39.21.41.91.4732 × 10 68.81.61.41.4128 × 10
CaseMaterialStructural ParameterRangeYield Strength
(MPa) σ

(MPa)
τ
acd (N) (Nm)
case1Structural Steel811.430010250129.821.92
case2AISI 104581250020350215.91.62
case3AISI 514081.62100040785480.91.63
Force DirectionSensitivity (mV/N)Cross Sensitivity Error (%)
(i = 1)3.3-0.230.280.05
(i = 2)2.70.04-0.630.03
(i = 3)1.60.450.43-0.07
(i = 4)104.1 (mV/Nm)0.020.140.31-
CaseSpindle Speed (rpm)Cutting Depth (mm)Feed Speed (mm/min)
case111100.2262
case211100.4262
case311100.6262
case413800.6262
case516800.6262
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Share and Cite

Wang, Q.; Wu, W.; Zhao, Y.; Cheng, Y.; Liu, L.; Yan, K. Design and Research of a Strain Elastic Element with a Double-Layer Cross Floating Beam for Strain Gauge Wireless Rotating Dynamometers. Micromachines 2024 , 15 , 857. https://doi.org/10.3390/mi15070857

Wang Q, Wu W, Zhao Y, Cheng Y, Liu L, Yan K. Design and Research of a Strain Elastic Element with a Double-Layer Cross Floating Beam for Strain Gauge Wireless Rotating Dynamometers. Micromachines . 2024; 15(7):857. https://doi.org/10.3390/mi15070857

Wang, Qinan, Wenge Wu, Yongjuan Zhao, Yunping Cheng, Lijuan Liu, and Kaiqiang Yan. 2024. "Design and Research of a Strain Elastic Element with a Double-Layer Cross Floating Beam for Strain Gauge Wireless Rotating Dynamometers" Micromachines 15, no. 7: 857. https://doi.org/10.3390/mi15070857

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COMMENTS

  1. PDF Test Cross Worksheet (A

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  2. Test Cross

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  7. PDF BIO102 Test Cross

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    Cutting force is one of the most basic signals that can reflect the information of the cutting process, so it is very necessary to study the strain elastic element of strain gauge wireless rotating dynamometers. This paper proposes a strain elastic element with a double-layer cross floating beam that can be applied to the strain gauge wireless rotating dynamometer, which can simultaneously ...