Question

Genetics

I was wondering how female calico cats express both an x chromosome with the orange trait and one x chromosome with the black trait if x inactivation occurs? If one of her x chromosomes is inactivated then wouldn't just that one color be left to be expressed? Also are all labrador retrievers carriers of the "e" chromosome? Does epistasis occur so the gene can't express pigment?

Thanks for any help!!

Answer 1

Fur colour in calico cat is X linked. As female have more than 1 X chromosome, inactivation occurs. So based of inactivation which chromosome (coding or range or yellow) coat colour determined and random inactivation of either of them results to patchy distribution of colour. This is an example of dosase compensation where to avoid effect of double dose of X chromosome, inactivation of single chromosome occurs through process doses compensation. This occur while embryo development and due to silencing enzymes, and their act at different time of development and mechanism of actions.

True, black for labrador is govern by BBEE; yellow by bbee; black with yellow by BbEe.

In detail, B = black; b= chocolate; E = ability to express dark coat pigment colour; and e = inability to express dark pigmentation. One more allele C responsible for red colour. Further, B (black) is dominant over B (chocolate) and yellow coat colour allele (e) is recessive when compared with E, but epistatic to B.