In experiments published in 1918 that sought to verify and expand the genetic linkage and recombination theory proposed by Morgan, Thomas Bregger studied potential genetic linkage in corn (Zea mays) for genes controlling kernel color (colored is dominant to colorless) and starch content (starchy is dominant to waxy). Bregger performed two crosses. In Cross 1, pure-breeding colored, starchy-kernel plants (C1 Wx/C1 Wx) were crossed to plants pure-breeding for colorless, waxy kernels (c1 wx/c1 wx). The F₁ of this cross were test-crossed to colorless, waxy plants. The test-cross progeny were as follows:
In Cross 2, plants pure-breeding for colored, waxy kernels (C1 wx/C1 wx) and colorless, starchy kernels (c1 Wx/c1 Wx) were mated, and their F₁ were test-crossed to colorless, waxy plants. The test-cross progeny were as follows:
For each set of test-cross progeny, determine whether genetic linkage or independent assortment is more strongly supported by the data. Explain the rationale for your answer.

Question

In experiments published in 1918 that sought to verify and expand the genetic linkage and recombination theory proposed by Morgan, Thomas Bregger studied potential genetic linkage in corn (Zea mays) for genes controlling kernel color (colored is dominant to colorless) and starch content (starchy is dominant to waxy). Bregger performed two crosses. In Cross 1, pure-breeding colored, starchy-kernel plants (C1 Wx/C1 Wx) were crossed to plants pure-breeding for colorless, waxy kernels (c1 wx/c1 wx). The F₁ of this cross were test-crossed to colorless, waxy plants. The test-cross progeny were as follows:

In Cross 2, plants pure-breeding for colored, waxy kernels (C1 wx/C1 wx) and colorless, starchy kernels (c1 Wx/c1 Wx) were mated, and their F₁ were test-crossed to colorless, waxy plants. The test-cross progeny were as follows:

Calculate the recombination frequency for each of the progeny groups.

Table showing phenotypes and their corresponding numbers from genetic experiments on corn.

In Cross 2, plants pure-breeding for colored, waxy kernels (C1 wx/C1 wx) and colorless, starchy kernels (c1 Wx/c1 Wx) were mated, and their F₁ were test-crossed to colorless, waxy plants. The test-cross progeny were as follows:

Table displaying phenotypes and their corresponding numbers from genetic experiments on corn.

For each set of test-cross progeny, determine whether genetic linkage or independent assortment is more strongly supported by the data. Explain the rationale for your answer.

Accepted Answer

Hello, everyone and welcome to today's video. So in experiments published in 1933 Barbara mcclintock studied potential genetic linkage in corn for genes controlling kernel color and endosperm composition. So now my kling to perform two crosses in the first class pure breeding color starchy can kernel plants were crossed to plants pure breeding for Colonna, sugary kernels. The F one of these crops were tests crossed to colorless and sugary plants and the test cross progeny were as follows or D F two generation. The phenotype number for color starchy, colorless, sugary, color, sugary and colorless starchy are given for a total of 1482 individuals. Now, considering the given data, which of the following statements is therefore true answer choice. A we have the genes are not linked. B the genes are on separate chromosomes. C, the genes are linked. D the genes are too far from each other. Now, in order to solve this problem, there is something fairly simple that we need to understand. Now, if the two genes are on different chromosomes or they are not linked, they will assort independently during meiosis and the expected phenotypic ratios will be 1 to 1 to 1 to 1 for the four possible combinations of the traits that we have here. Now, if the genes are close together or are linked on the same chromosome, they all tend to be inherited together. And the expected phenotypic ratio will deviate or will be very far apart from this 1 to 1 to 1 to 1. That is not what we will be seeing. Now, if we look at the statistics, if we look at the phenotype number that we are given for each of the treats, we have 731 28 9. This is not a 1 to 1 to 1 to 1 ratio. It is very deviated from that which indicates that the genes are going to be linked and four, the correct answer for this question is going to be see the genes are linked. I really hope this video helped and I hope to see you on the next one.

Verified video answer for a similar problem:

Key Concepts

Genetic Linkage

Independent Assortment

Test Cross