A Geneticist Is Examining a Culture of Fruit Flies and Discovers

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The Answer is The inheritance of the melanotic mutation in fruit flies can be explained by the fact that the mutation is located on the X chromosome. Since the cross produces twice as many female progeny as male progeny, this suggests that the melanotic mutation is recessive and located on the X chromosome.

When a female melanotic fly is crossed with a normal male, the resulting progeny show that the melanotic trait is inherited in a sex-linked manner. This means that the melanotic gene is located on the X chromosome, and since females have two X chromosomes, they can be carriers of the mutation without showing the phenotype. However, males only have one X chromosome, so if they inherit the melanotic mutation, they will exhibit the phenotype.

The fact that melanotic females are frequently obtained in subsequent crosses with normal males, but never any melanotic males, further supports the idea that the melanotic mutation is located on the X chromosome. This is because males only inherit one X chromosome from their mother, so if the X chromosome carries the melanotic mutation, they will exhibit the phenotype. However, since females have two X chromosomes, they have a higher chance of being carriers of the mutation without showing the phenotype.

In conclusion, the inheritance of the melanotic mutation in fruit flies can be explained by its location on the X chromosome, leading to a sex-linked inheritance pattern. This explains why melanotic females are frequently obtained in subsequent crosses with normal males, but never any melanotic males.

A Geneticist Is Examining a Culture of Fruit Flies and Discovers

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