The fruit fly Drosophila melanogaster has a haploid chromosome number of n = 4,

Question

The fruit fly Drosophila melanogaster has a haploid chromosome number of n = 4, and 2n = 8 Chromosome IV in this species is a tiny autosome. Flies trisomic for chromosome IV 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 recessive to 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 these two loci: Express your answer as a fraction (example: 3/5). 0.500 If this trisomic male is crossed with a (ey^- ey^-, gw^- gw^-) female, what proportion of the progeny will be phenotypically gawky? Express your answer as a fraction (example: 3/5).

Explanation / Answer

the proportion of progeny that will be phenotypically gawky=(ey +ey+gw+gw /4 )x100

=(2(ey+gw)/ 4)x100

=>(ey+gw )/2 x100

=>50(ey+gw)=>50%=1/2

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