After decades of detective work, geneticists have pinpointed the mutation that turns some house-cats into ginger tabbies. A small missing stretch of DNA in a regulatory region near the ARHGAP36 gene on the X chromosome greatly increases the gene’s activity in pigment-making cells, shifting coat color toward reddish-yellow tones – orange cats.
Because the mutation sits on the X chromosome, its effects differ by sex: males, with only one X, become fully orange when they inherit the altered segment, while females need two copies to be completely ginger. Most females therefore display the familiar calico or tortoiseshell patchwork created when one of their two X chromosomes is randomly switched off in each skin cell.
The two independent studies that cracked the mystery used modern cat genome databases and tissue samples to trace the colour change to this single regulatory “cut-out”. Although ARHGAP36 is linked to developmental problems in other species, researchers found no evidence that the orange mutation affects feline health or behaviour.
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