You notice that in most biology and genetics textbooks, the authors show that Gregor Mendel used flower color as one of his pairs of traits. The purple flower phenotype is dominant to the white flower phenotype.
However, if you go back to Mendel's experiments, you see that he actually studied seed coat color. The purple seed coat phenotype was dominant to the white seed coat phenotype. Mendel did note that plants with purple seed coats had purple flowers and plants with white seed coats had white flowers.
Is the gene for seed coat color pleiotropic because it also affects flower color, or are the seed coat color gene and the flower color gene very closely linked? To find out the answer to this question, you assume that the genes for flower color and seed coat color are different genes, and your null hypothesis is that they assort independently. You designate the flower color gene wf and the seed coat color gene sw. Plants that are WF__, SW___ have purple flowers and purple seed coats. Plants that are wf wf, ws ws have white flowers and white seed coats.
You do the testcross WF wf, SW sw X wf wf, sw sw and collect 15,206 offspring. What result would tell you that the wf and sw loci are probably the same, pleiotropic locus?
A. One of the offspring had white flowers and purple seed coats.
B. About half of the offspring had purple flowers and purple seed coats, and all the rest had white flowers and white seed coats
C. All of the offspring had purple flowers and purple seed coats.
D. None of the offspring had white flowers and white seed coats.
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