If this trisomic male is crossed with a ( e y e y , g w g w ) female, what propo
ID: 215665 • Letter: I
Question
If this trisomic male is crossed with a (ey ey , gw gw ) female, what proportion of the progeny will be phenotypically eyeless?
Express your answer as a fraction (example: 3/5). Please see image for additional information that may be needed.
The fruit fly Drosophila melanogaster has a haploid chromosomenumber of n 4 and 2n 8. Chromosome V in this species is a tiny autosome. Flies trisomicfor chromosomeIV are fertile and have no apparent defects. The eyeless (ey) and gawky (gw) loci are tightly linked on chromosome IV. Loss-of function ey- and gw-alleles are recessiveto ey and gw, respectively. Flies homozygous for ey-lack eyes, and flies homozygous for gw- have disrupted circadian rhythms. Consider a male fly trisomic for chromosome IV, with each of the three chromosome copies bearing different allele combinations for thesetwo loci: ey gw- ey+ gw- ey- gw+Explanation / Answer
The male would produce the following gametes:
and the female would produce following gametes:
after the cross between these, they would provide the following progeny:
The eyeless progeny should have ey-ey-.
The fraction of the progeny which would be eyeless is: 50% or 1/2