Question 9

(Multiple Choice)

Dr.Disney has been raising exotic fruit flies for decades.Recently, he discovered a strain of fruit flies that in the recessive condition have baby blue eyes that he designates as bb.He also has another strain of fruit flies that in the recessive condition have pink wings that are designated as pw.He is able to establish flies that are homozygous for both mutant traits.He mates these two strains with each other.Dr.Disney then takes phenotypically wild-type females from this cross and mates them with double recessive males.In the resulting testcross progeny, he observes 500 flies that are of the following make-up: Dr.Disney has been raising exotic fruit flies for decades.Recently, he discovered a strain of fruit flies that in the recessive condition have baby blue eyes that he designates as bb.He also has another strain of fruit flies that in the recessive condition have pink wings that are designated as pw.He is able to establish flies that are homozygous for both mutant traits.He mates these two strains with each other.Dr.Disney then takes phenotypically wild-type females from this cross and mates them with double recessive males.In the resulting testcross progeny, he observes 500 flies that are of the following make-up:   Assuming the wild-type alleles for these two genes are b+ and pw+, what is the CORRECT testcross of the F1flies? A)bb<sup>+</sup> pw<sup>+</sup>/bb pw × bb pw/bb pw B)bb<sup>+</sup> pw<sup>+</sup>/bb pw × bb pw<sup>+</sup>/bb<sup>+ </sup>pw C)bb<sup>+ </sup>pw/bb pw<sup>+</sup> × bb pw/bb pw D)bb<sup>+</sup> pw/bb pw<sup>+</sup> × bb<sup>+</sup> pw<sup>+</sup>/bb pw E)bb<sup>+</sup> pw<sup>+</sup>/bb pw × bb<sup>+</sup> pw/bb pw<sup>+</sup> Assuming the wild-type alleles for these two genes are b+ and pw+, what is the CORRECT testcross of the F1 flies?


A)bb+ pw+/bb pw × bb pw/bb pw
B)bb+ pw+/bb pw × bb pw+/bb+ pw
C)bb+ pw/bb pw+ × bb pw/bb pw
D)bb+ pw/bb pw+ × bb+ pw+/bb pw
E)bb+ pw+/bb pw × bb+ pw/bb pw+

Answer