Tortoiseshell calico skin#
Pigment genes are expressed in melanocytes that migrate to the skin surface later in development. Cells in which the non-orange ( o) allele is inactivated express the orange ( O) allele. Cells in which the chromosome carrying the orange ( O) allele is inactivated express the alternative non-orange ( o) allele, determined by the (B) gene.
“ The cells of female cats, which like other mammalian females have two X chromosomes (XX), undergo the phenomenon of X-inactivation, in which one or the other of the X-chromosomes is turned off at random in each cell in very early development. A cat would need to inherit two X chromosomes – 1 with the orange code and 1 with the black code – in order to display the coat.Īnd then, the cells would have to undergo a process called X-inactivation to produce the brindled appearance of orange and black coloring of torties. However it’s a bit more complicated than this since obviously not all female cats have the coat coloring of a calico or tortoiseshell.
So if a cat gets the XY chromosomes, it will be male, and if it gets the XX chromosomes, it will be female.īecause the orange and black color code is attached to the X chromosome, calicos and torties need the double X chromosomes in order to have a chance of displaying the classic coat coloring. The sex chromosomes X and Y determine whether a cat will be male or female. The reason for this comes down to genetics. About 1 in every 3,000 calicos and 1 in every 3,000 torties is born male.
Tortoiseshell cats are largely black/brown with orange/reddish orange coloring mixed in to varying degrees.
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