The patch (Ph) locus allele, patch-extended (Phe),
has significantly less pigmentation than the
original mutation and homozygotes have been known to survive to term. Analysing
subspecific F1 hybrids, we were able to demonstrate that Phe
is a deletional mutation
encompassing the platelet-derived growth factor receptor alpha subunit
(Pdgfra). The deletion does
not appear to extend into the coding sequence of the Kit gene
(a related tyrosine kinase receptor).
However, we were able to demonstrate that, while the Kit gene
is transcribed, it does not encode a
functionally active receptor.