None of the females 1/2 of the females All of the females Either 1/2 or none of

Question

None of the females

1/2 of the females

All of the females

Either 1/2 or none of the females depending on whether the black male cat was homozygous for black or heterozygous.

X-inactivation in mammals can lead to mosaic coloration if the gene governing coat color is on the X chromosome. This occurs with cats and can lead to the calico coat color on the back, a mosaic of orange and black patches. If a calico coat female and a black coat male mate and have kittens, what fraction of their female kittens will have a calico coat?

None of the females

1/2 of the females

All of the females

Either 1/2 or none of the females depending on whether the black male cat was homozygous for black or heterozygous.

Explanation / Answer

Female cat have two X chromosome. Very early embryogenesis, at 64 cell stage, one X chromosome is inactivated in each cell. The gene for coat color in cats is located on the X chromosome. In female one gene for coat pigmentation is silence when X is inactivated. If a female can get an orange gene from one parent and a black gene from father, kittens become hetrozygous, the cat will have some cell with orange working gene and other cell have black worrking geene, both gene one from father and one from mother anre present, While only one use in each cell because one X becomes inactivated by mechanism, including DNA methylation, histone modification and coating by XIST RNA.

Yet kittens can pass either orange gene or the black gene to each her babies and each kittens will not have same inactivation pattern. The male kittens have only one X chromosome either from father or from mother so male will havi either black or calico coat color. The female kitten can be either all black depending on what chromosome get from father (Black coat color) or black and orange like her if ggot from mother and will not be inactivated.

So the answer will be either 1/2 or none of thee females depending on whether the black male cat was homozygous for black or heterozygous.

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