* Genetics: Calico coloration is determined by the X chromosome. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). The genes for black, orange, and white fur are located on the X chromosome.
* The calico pattern: To be calico, a cat needs at least two different color genes on its X chromosomes. This is why female cats are much more likely to be calico, as they have two X chromosomes to inherit these genes.
* The rare exception: A male cat can only be calico if he has an extra X chromosome (XXY), which is a genetic condition called Klinefelter syndrome. This is extremely rare, occurring in approximately 1 in 1,000 male cats.
Therefore, while it's not impossible for a male cat to be calico, it's incredibly rare and almost always signifies the presence of Klinefelter syndrome.