An experiment was conducted with Drosophila flies carrying recessive white-eye and yellow-body alleles. The white and yellow genes are on the X-chromosome. The parental (P₀) individuals were homozygous white-eye, normal body female and red-eye, yellow-body male. F₁ females had a wild-type phenotype and F₁ maleshad normal bodies and white eyes. F₁ individuals were then mated. What phenotypes are expected in the F₂ generation? Please select all that apply.

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Quizplus · Accepted Answer

The white and yellow genes are on the X-chromosome, and so are linked. The parental X-chromosomes have w/w y⁺/y⁺ (female) and w⁺/_ y/_ (male). The + symbol denotes wild-type. This means that here, the w allele is linked to the y⁺allele and the w⁺allele is linked to the y allele. F₁ females are w⁺/w y⁺/y. F₁ males are w/_ y⁺/_. Therefore, the majority of F₂males will be w/_ y⁺/_ (white-eye, normal body) or w⁺/_ y/_ (red-eye, yellow body). Rarely, a crossover will occur between the white and yellow genes to give males with w⁺/_ y⁺/_ (wild-type) or w/_ y/_ (white-eye, yellow body). This means that very few males (w⁺/_ y⁺/_) will have a wild-type phenotype. 50% of males have white eyes. The majority of F₂ females will be w⁺/w y+/y (wild-type) or w/w y⁺/y⁺(white-eye, normal body). Rarely, a crossover will occur between the white and yellow genes to give females with w⁺/w y⁺/y⁺(wild-type) or w/w y⁺/y (white-eye, normal body). Together, ~50% of female flies are wild-type and 50% are white-eye, normal body. Thus, 100% of females have a normal body and 50% have white eyes.

An Experiment Was Conducted with Drosophila Flies Carrying Recessive White-Eye