The coat of the normal cat consists of three hair types: long and straight guard hairs of uniform diameter, thinner fawn hairs, and fine undulating down hairs of uniform thickness. In general, shorthair is dominant to longhair. Four separate mutations are detected in the feline FGF5 locus that may have arisen independently in geographically isolated, freeranging populations of domestic cats and increased in frequency through natural selection in cold climates where the long-haired trait might be advantageous. Shorthaired cats sometimes produce longhairs due to a recessive gene. Such carriers, and their offspring, are often removed from the breeding programme to eliminate undesirable recessives. Longhaired cats have two recessive genes for the longhaired trait and should always breed true for longhair.
Kehler, J.S., David, V.A., Schäffer, A.A., Bajema, K., Eizirik, E., Ryugo, D.K., Hannah, S.S., O’Brien, S.J., and Menotti-Raymond, M. (2007). Four independent mutations in the feline fibroblast growth factor 5 gene determine the long-haired phenotype in domestic cats. J. Hered. 98, 555–566.