In tomatoes, the allele T for tall plant height is dominant to dwarf allele t, the P allele for smooth skin is dominant to the p allele for peach fuzz skin, and the allele R for round fruit is dominant to the recessive r allele for oblong fruit. The genes controlling these traits are linked on chromosome 1 in the tomato genome, and the genes are arranged in the order and with the recombination frequencies shown.
What are the genotypes of gametes produced by the F₁, and what is the predicted frequency of each gamete?

Question

In tomatoes, the allele T for tall plant height is dominant to dwarf allele t, the P allele for smooth skin is dominant to the p allele for peach fuzz skin, and the allele R for round fruit is dominant to the recessive r allele for oblong fruit. The genes controlling these traits are linked on chromosome 1 in the tomato genome, and the genes are arranged in the order and with the recombination frequencies shown.

What are the genotypes of gametes produced by the F₁, and what is the predicted frequency of each gamete?

Genetic linkage diagram showing genes T, P, R with recombination frequencies of 0.04 and 0.18.

What are the genotypes of gametes produced by the F₁, and what is the predicted frequency of each gamete?

Accepted Answer

Hey, everyone. Let's take a look at this question together in guinea pigs, the allele for short hair is dominant over the allele for long hair and the allele for white color is dominant over the allele for black color. We then cross a guinea pig that is heterozygous for both traits with a tester and they produce the following offspring with parental configuration, 1 45 with parental configuration, 2 51 recombinant, 1 15 and recombinant 2 10. What does this tell us in terms of genetic linkage? Is it answer choice? A gene S is linked to gene W, answer choice B gene S is not linked to gene W, answer choice C gene S and gene W is perfectly linked or answer choice D, none of the options is correct. Let's work this problem out together to try to figure out which of the following answer choices is the correct answer. So we know that we have a cross involving a parent that is heterozygous for both traits. So we have our parent one which is heterozygous for both traits. So we have heterozygous S and heterozygous W for our parent one. And then we know we are crossing them with a tester. And the tester means that they are homozygous recessive for both traits. So, we have our parent two, which is that tester and is homozygous recessive for both traits. So we have homozygous recessive S and homozygous recessive. W and so we have our cross of that heterozygous S and heterozygous, W for parent one with the homozygous recessive S and homozygous recessive, W for parent two, which the cross that is that f one generation, the F one progeny yields or different genotypes which are heterozygous S and heterozygous W, heterozygous S and Homozygous recessive W homozygous recessive S and heterozygous W. And lastly, we have homozygous recessive SS and homozygous recessive W which we know that the heterozygous S and heterozygous W genotype is that parent, one genotype. So we have our parent, one genotype and then our parent two, which is the tester that is homozygous recessive or both. S and W is our parent two genotype. So we have our parents. So these are the parent genotypes, which means that the remaining two genotypes are our recombinant. And from the number of offspring, we can see that with the parental configuration one, we have 45 with parental configuration two, we have 51. But when it comes to the recombinant, we only have 15 for recombinant one and 10 for recombinant two, which means that we do not have an equal shift of offspring between both parental configurations and recombinant and the parental configuration, genotypes are the ones that are the most numerous, which we know that in our parent genotypes, we have a dominant allele present in both S and W or no dominant allele present in both S and W. Whereas when it comes to our recombinant, we have only one S or one W dominant allele, which means that gene S and gene W are linked because our parent genotypes have either one S and one W ali dominant or one S and one W allele recessive, which means that gene S and gene W are linked and answer choice. A gene S is linked to gene W is the correct answer because from the cross of our parent, one that is heterozygous four S and heterozygous for W with parent two, that is homozygous recessive four S and homozygous recessive four W we are able to see that the offspring with either parental configuration, meaning that they have both S and N W having at least one dominant allele or both S N W having zero dominant alleles. Those are the genotypes that are the most numerous and the recombinant are the least numerous, which is the case for when gene S and G W are linked. So, answer choice. A gene S is linked to gene W is the correct answer. I hope you found this video to be helpful. Thank you and goodbye.

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Key Concepts

Dominant and Recessive Alleles

Linkage and Recombination

Gamete Formation and Genotype Frequencies