Question

Da Bait University was the first to successfully clone a cat and her name was CC. She was not identical to her predecessor, rainbow, but the researchers were able to prove that her DNA was indeed the same. What factors contributed to the difference between Rainbow and her clone CC?

A) X inactivation of the black allele

B) both environmental effects on white spotting and X inactivation of the black allele

C) Both environmental effects on white spotting and X inactivation of the orange allele

D) X inactivation of the orange allele

E) the dominant white allele disrupted by a transposon in CC

Answer 1

The factor that contributed to the difference between rainbow and her clone CC is

Ans. (D) X inactivation of orange allele

Rainbow was a calico, with grey and orange spots; the new kitten CC or Carbon Copy, had grey spots with no trace of orange at all. The scientists explained this difference by the process of X chromosome inactivation.

All calico cats are females. Glenes for black and grey spots, and the genes for orange spots, are present on the X chromosome. So a cat needs two X’s to have both black and orange spots. But, in any spot only one gene is active, that means the orange spots have inactive black genes, and the black spots have inactive orange genes.

While selecting a cell from Rainbow, the scientists picked a cell that only had the active gene for grey spots. That resulted in a cat with no ability to form orange spots was born.