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Red is a sex linked gene. The red gene is only carried
on the x (female) chromosome. All females are xx, where as males are xy.
Each cell during development "turns off" the coding for one of
the x chromosomes in every female. This on/off is random... as is
evident in the random speckles and spots in the torties. In the cells
where one x chromosome has the red gene and the other x chromosome does
not, those cells that have the chromosome carrying red "turned
on" will be red, the cells that have the chromosome carrying
red "turned off" will be seal. This is how a female that has
one red gene Oo will be a tortie. A female that has two red genes will
be red OO, It does not matter which chromosome is turned on or off in
each cell... since they both have the red gene. Since males are the
combination of one x chromosome and one y chromosome, they only need one
red gene to be red. There is not the issue of one chromosome being
inactivated since the males are xy not xx.
Red is produced when a biochemical process substitutes
the eumelanin (black and all derived colors) with phaeomelanin as the
hair is developing. That gives a lighter pigment grain which we perceive
as red. Another fact with the red is that both tabby (agouti) (A) and
solid (non-agouti) (a) look the same. The non-agouti (a) gene
works by depositing eumelanin on the ends of all the hair shafts,
"filling in" the background with the same color as the dark
stripes. The tabby stripes then disappear. In a red cat, there is
no eumelanin produced. The tabby markings can not disappear. This
explains why reds always show pattern, but may never produce agouti
kittens. To improve the color density, appearance of no stripes and
shade of red, you must manipulate the group of modifiers, which are
better known as polygenes. They are responsible for the deep red color,
and what appears to be a lack of striping. |
