The boss in your laboratory has just heard of a proposal by another laboratory that genes for eye color and the length of body bristles may be linked in Drosophila. Your lab has numerous pure-breeding stocks of Drosophila that could be used to verify or refute genetic linkage. In Drosophila, red eyes (c⁺) are dominant to brown eyes (c) and long bristles (d⁺) are dominant to short bristles (d). Your lab boss asks you to design an experiment to test the genetic linkage of eye color and bristle-length genes, and to begin by crossing a pure-breeding line homozygous for red eyes and short bristles to a pure-breeding line that has brown eyes and long bristles.

In your experimental design, what are the genotype and phenotype of the line you propose to cross to the F₁ to obtain the most useful information about genetic linkage between the eye color and bristle-length genes? Explain why you make this choice.

Question

In your experimental design, what are the genotype and phenotype of the line you propose to cross to the F₁ to obtain the most useful information about genetic linkage between the eye color and bristle-length genes? Explain why you make this choice.

Accepted Answer

Hello, everyone. And welcome to today's video. We observed that in the garden, the green seeded between parenthesis, capitalized G peas are dominant or jealous seeded between parenthesis, lower case G peas and purple flowers between parentheses, capitalized P peas are dominant over white flour between parentheses, lower case P P. Now we conducted an experiment by crossing the dominant true breeding piece and the recessive true breeding piece and obtained hetero offspring. Now, which of the following genotypes can we use to cross with these F1 heterozygous or die hybrid to determine the genetic linkage of the two genes? So for these, we are going to be first of all conducting a test cross. So we need to determine which of these genotypes that we have here in the answer choices can be used in the tacos. So as answer choice A, we have fully homozygous dominant GMP. As answer choice B, we have heterozygote G and heterozygous P as answer choice C, we have homozygote dominant G and homozygote recessive P. And as answer choice D we have fully homozygous recessive GMP. Now remember that when we have a test sros, we have the non tester which we know is going to be hetero for both G and P. So that is going to be, they're a genotype. Now, in the test cross, we have the actual test genotype that we're going to be using. The test, the one that we know the genotype for. And this is always going to be a homo recessive organism or a true breeding homozygous recessive organism. So in this case, we're going to be needing a genotype that is fully homozygous recessive in order to participate in the test cross. Therefore, the genotype is going to be fully homozygous recessive for GMP or answer choice D which is fully homozygous recessive for G and P. I really hope this video helped you and I hope to see you on the next one.

Verified video answer for a similar problem:

Key Concepts

Genetic Linkage

Drosophila Genetics

Punnett Square and F1 Generation