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.