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In a Drosophila experiment, a cross was made between homozygous wild-type females and yellow-bodied males. All of the resulting F₁s were phenotypically wild type. However, adult flies of the F₂ generation (resulting from matings of the F₁s) had the characteristics shown in the figure. How is the mutant allele for yellow body inherited?
A) It is recessive.
B) It is codominant.
C) It is dominant.
D) It is incompletely dominant.

Question

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In a Drosophila experiment, a cross was made between homozygous wild-type females and yellow-bodied males. All of the resulting F₁s were phenotypically wild type. However, adult flies of the F₂ generation (resulting from matings of the F₁s) had the characteristics shown in the figure. How is the mutant allele for yellow body inherited?
A) It is recessive. 
B) It is codominant. 
C) It is dominant. 
D) It is incompletely dominant.

Quizplus · Accepted Answer

All of the F₁s were phenotypically wild type, which means they must have been heterozygous for the yellow body allele. This indicates that the yellow body allele is recessive to the wild-type allele. The F₂ generation shows a classic 3:1 ratio expected for a single gene with a recessive allele.

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