calico cat shows random distribution of orange and black patches of fur.
The gene for this locus is X-linked. Since the inactivation of X chromosomes occurs
randomly early in embryonic development,
all progeny cells from the embryonic precursor cell have the same X chromosome inactivated,
causing a patchy expression of the alleles.
The white patches are due to a separate epistatic "spotting gene"
that prevents pigments from migrating to the skin.