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.
The F₁ are test-crossed to dwarf, peach fuzz, oblong plants, and 1000 test-cross progeny are produced. What are the phenotypes of test-cross progeny, and what number of progeny is expected in each class?

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.

The F₁ are test-crossed to dwarf, peach fuzz, oblong plants, and 1000 test-cross progeny are produced. What are the phenotypes of test-cross progeny, and what number of progeny is expected in each class?

Gene arrangement and recombination frequencies for tall, smooth, and round traits in tomatoes: T 0.04, P 0.18, R.

The F₁ are test-crossed to dwarf, peach fuzz, oblong plants, and 1000 test-cross progeny are produced. What are the phenotypes of test-cross progeny, and what number of progeny is expected in each class?

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, the offspring will have the following genotypes except which is it answer choice. A heterozygous S heterozygous W answer choice B, heterozygous S homozygous recessive W answer choice C homozygous recessive S heterozygous W or answer choice D homozygous dominant S and homozygous dominant. W let's work this problem out together to try to figure out which of the following genotypes are not found within the offspring of the cross for the guinea pig. So in order to solve this question, we first must figure out the different genotypes that were used in the cross so that we can set up a pun a square to figure out the genotypes of the offspring. And we know that we are crossing a guinea pig that is heterozygous for both traits, which means that parent one is heterozygous for both S and W. So we have that heterozygous S and heterozygous W and then we know that parent two, which is the tester has that homozygous recessive genotype for both traits. So they must be homozygous recessive for S and homozygous recessive for W which means that the genotypes involved in the cross are heterozygous S, heterozygous W and Homozygous recessive S and Homozygous recessive W. So now that we know the genotypes of the parents, we can go ahead and set up a punt square to determine all of the genotypes or their offspring. And so now that we have set up our puit square where we have that parent one on the top of the pundit square and parent two on the left side of the pundit square, which we obtained the different combinations of the alleles by distributing the alleles that are found within the genotypes or both parents. And so that is how we set up our puit square, which we can go ahead and cross parent one with parent two to obtain all of the genotypes or their offspring. And after the cross between parent, one and parent two, we are able to determine that their offspring have four different genotypes which those f one genotypes or the offspring or heterozygous S and heterozygous W. Heterozygous S, homozygous recessive W, homozygous recessive S and heterozygous W and lastly, homozygous, recessive S and homozygous recessive W so the offspring of the cross between parent, one and parent two yields four different genotypes. And so looking at our answer choices, we can determine which of the following genotypes are found within the offspring. And so answer choice A is that heterozygous S and heterozygous, W which we know is present in the offspring. So answer choice A is found among the offspring. Answer choice B says heterozygous, S and Homozygous recessive, W which we know is also found among the offspring. So answer choice B is present. Answer choice. C says Homozygous recessive S and heterozygous, W which we know is also found in the offspring. So answer choice C is present and answer choice. D says Homozygous dominant, S and Homozygous dominant, W which we know is not found among the offspring of that parent, one and parent two cross. Since we know it is not possible to have that homozygous dominant or S or for W since we only have one parent with a dominant allele for S and W and the other parent only has those recessive alleles. So answer choice D is not a possible genotype, which means that answer choice D Homozygous dominant, S and Homozygous dominant. W is the correct answer because it is one of the following genotypes that is not found among the cross between parent, one and parent two. Since we know that parent, one has that heterozygous S and heterozygous W and parent two is homozygous recessive for both S and W and so we have a cross between parent, one with that heterozygous S and heterozygous W and parent two with the homozygous recessive S and homozygous recessive W which yields four different types of genotypes in their offspring. Of which answer choice. D homozygous dominant, S and homozygous dominant. W is not one of them. So answer choice. D 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

Test Cross