You have discovered a new orange body color gene on the X chromosome of Drosophi

Question

You have discovered a new orange body color gene on the X chromosome of Drosophila similar to the gene that confers orange coat color in cats. You know that X chromosome inactivation in female cats heterozygous for the coat color gene can result in tortoiseshell colored coats.

A) Do you expect to see similar tortoiseshell body color in a heterozygous female Drosophila? Explain your answer?

B) If you found the same gene in a kangaroo, would you expect to see the tortoiseshell pattern in a heterozygous female?

Explanation / Answer

Tortoiseshell cats have two different alleles of an X-linked gene: X+(non-orange, or black) and Xo(orange). The patchy distribution results from X-inactivation during early embryo development. Each cell of the early embryo randomly inactivates one of the two X chromosomes, and the inactivation is maintained in all of the daughter cells. So each patch of black fur arises from a single embryonic cell that inactivated the Xo, and each patch of orange fur arises from an embryonic cell that inactivated the X+.

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