If a female Drosophila that is heterozygous for a recessive X-linked mutation is
ID: 79526 • Letter: I
Question
If a female Drosophila that is heterozygous for a recessive X-linked mutation is crossed to a mutant male, what proportion of progeny will have the mutant phenotype? 0 1/2 1/4 3/4 2/3 If a female Drosophila that is heterozygous for a recessive X-linked mutation is crossed to a mutant male, what proportion of progeny will have the mutant phenotype? If a female Drosophila that is heterozygous for a recessive X-linked mutation is crossed to a mutant male, what proportion of progeny will have the mutant phenotype? 0 1/2 1/4 3/4 2/3Explanation / Answer
Zero percent.
XwX Female cross with XYc (mutant male)
results are XwX, XwYc , XwX, XYc
In fruit flies, the Y chromosome is structurally different from the X chromosome, and it doesn’t carry genes that are complementary to those on the X, so any gene that is on the X in a male will be expressed, while the regular rules of dominant and recessive inheritance apply to female flies because they carry two X chromosomes. A white-eyed male must have the white mutation on its single X chromosome. In a female fly, the white mutation is inherited recessively, so two copies of the white mutation are necessary to produce a white-eyed female.
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