For decades scientists have observed that cats with completely ginger colouring are far more likely to be male. This tallies with the fact that the gene is carried on the X chromosome.
Chromosomes are larger sections of DNA, and male cats like other mammals have an X and a Y chromosome, which carry different number of genes.
As it is a gene only on the X chromosome, in this case controlling the pigment production, then one missing piece of DNA is enough to turn a cat fully ginger.
In comparison female cats have two X chromosomes so the DNA needs to be missing in both chromosomes to increase lighter pigment production to the same extent – it means a mixed colouring is more likely.
“These ginger and black patches form because, early in development, one X chromosome in each cell is randomly switched off,” explains Prof Hiroyuki Sasaki, geneticist at Kyushu University.
“As cells divide, this creates areas with different active coat colour genes, resulting in distinct patches.”