A mutant gene that produces brown eyes bw is located on chromosome #2 of Drosophila melanogaster,whereas a mutant gene producing bright red eyes,scarlet st ,is located on chromosome #3.Phenotypically,wild- type flies with dull red eyes ,whose mothers had brown eyes and whose fathers had scarlet eyes,were mated.The 800 offspring possessed the following phenotypes: wild type dull red ,white,scarlet bright red),and brown.Most of the 800 offspring had wild- type eyes,whereas those with white eyes were the least frequent. From the information presented above,how many white- eyed flies would you expect in the F₂generation? A)200 B)450 C)350 D)50 E)150

Question

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The parents have the genotype FfSs (where F and S represent the wild-type alleles for eye color). When these are crossed, the offspring will have the genotype FfSs (wild-type), Ffss (white), ffSs (scarlet), or ffss (brown). According to the problem, white-eyed flies were the least frequent phenotype, so we can assume that there were very few Ffss individuals in the offspring. The frequency of FfSs, ffSs, and ffss individuals cannot be determined from the information given. Therefore, the expected number of white-eyed flies in the F1U1B12 S1U1B0generation is likely to be very low, maybe even zero. The most reasonable answer choice is D) 50, which is the lowest possible option.

A Mutant Gene That Produces Brown Eyes Bw Is Located