Manx cat

A tail-less Manx Cat (Tt)

    Tail-lessness in Manx cats (and other mammals) is due to a locus (T) that affects development of the post-axial skeleton. Cats with standard tails are tt. There is a series of dominant T alleles that lead to lesser or greater reduction of the tail. Manx cats often have other problems in development, such as paralysis of the hindquarters and prolapse of the rectum. The TT homozygote combination is lethal.

    Given the lethality of T, why does it remain in the population? The skeletal phenotype is a pleiotropic effect of another effect of the T locus, which  is segregation distortion. In Tt heterozygotes, the T allele is preferentially  segregated into sperm, such that the T : t ratio may be as high as 70:30 rather than the expected 50:50.

Text material ©2011 by Steven M. Carr