Assume that three pairs of autosomal alleles are found in Drosophila: x and+, y

Question

Assume that three pairs of autosomal alleles are found in Drosophila: x and+, y and +, and z and +. As shown by the symbols, each non- wild-type allele is recessive to its wild-type allele. A cross between females heterozygous at these three loci and males that exhibit all three recessive traits yields progeny having the following phenotypes: +650 xy z 661 xy+ 82 ++2 85 y+255 x z 262 +yz3 X++2 What is the correct gene order? 0 , 2-- O D. There is not enough information to make a correct determination

Explanation / Answer

First, identify the parents and the double cross over from the given phenotypes. The ones with the highest frequency will be the parents, +++(650) and xyz(661). The ones with the lowest frequency will be the double crossovers, +yz(3) and x++(2).

Then, compare the parents and double crossovers to see which gene has changed position. In this case, x has changed position.

Thus, the gene x will be present in the center.

When we see the given options, there is only one option with x in the center. Thus, the correct option is C. z--x--y

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