Question

Practice Genetics Problems SHOW ALL WORK IN THE SPACES BELOW EACH QUESTION. Monohybrid cross: Sex linkage 1. In fruit flies, eye color is sex linked. Red color is dominant to white. a) A red eyed male was crossed with a white eyed female. What are the expected phenotypic frequencies of the offspring with respect to gender and eye color? b) A white eyed male was crossed with a homozygous red eyed female; an F, female was then crossed with a red eyed male. What would be the expected phenotypic ratios in the offspring?

Answer 1

Monchybrid cross - sex linkage -eye colour is sex linked. That is genes for eye colour is X-linked - as red eye colour is dominant over white eye colour so male & female will have possible genotype as- il female] (i) R// R homozygous red eyed (i) R1r heterozygous red eyed homozygous white eyed (1) rllr (2) Male] [ red eyed - represent Y chromosome white eyed.

a) cross between red eyed male & white eyed female. Parent red eyed male x white eyed female genotype RII gametes → a fi generation I RI red eyed female white exed male I Rlr red eyed female white eyed male Phenotypic ratio- Red eyed female : White eyed male 1:1

b) cross between white eyed male & red eyed female parent white eyed male x red eyed female genotype rl X RIR gomates gametes ' © ®*® i generation RI RI ellr Rlr red, female red, female RIC red male red male Fa generation Allr x RM red, female red, male q RI R|lr RIIR red, female red female RENA RIA red, male white, male Phenotypic ratio red female: red, male : white, male 2 : 1:1