In Drosophila, the gene for scalloped wings (sd) is a sexlinked recessive and th
ID: 52309 • Letter: I
Question
In Drosophila, the gene for scalloped wings (sd) is a sexlinked recessive and the gene for shaven bristles (sv) is an autosomal recessive. A wild type female whose father was scalloped and shaven is mated with a shaven male.
A. What is the genotype of the male?
B. What is the expected proportion of wild type flies among the offspring?
C. What is the expected proportion of scalloped males among the offspring?
D. What proportion of the offspring are expected to be either shaven
females or scalloped males?
E. What is the probability that the first two offspring will be wild type females?
Please answer all of the questions if possible and provide explanations as to thought process. Thanks!
Explanation / Answer
Based on the given data,
The genotype of wild type female is: X+X sd (carrier)
A) The genotype of shaven male is: XY
A cross between X+Xsd and XY, gives
F1 = X Xsd, X+Y
F2 = X X+, X Y, X+ Xsd, Xsd Y
Thus, the ratio is: 1:1:1:1
B) The expected proportion of wild type flies among the offspring is: ½
C) The expected proportion of scalloped males among the offspring is: 1/4th
D) The offspring are expected to be either shaven females or scalloped males is ½