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.
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.