I am interested in how breeders of the Manx cat are able to create healthy cats. We know that the gene that causes taillessness in the Manx is a nasty gene, which potentially causes severe health problems in living Manx cats and which causes the death of embryos before birth.
Kittens die before birth when they are homozygous for the Manx gene. “Homozygous” means possessing a pair of identical alleles at a place (locus) on the chromosome. The Manx gene is symbolised by the capital letter “M” because It is dominant. The CFA say it is “incomplete dominant”.
At one time breeders were not aware that kittens were dying in the womb. I presume there was no evidence of their existence except that there was a decrease in the average number of young per litter when Manx mated Manx cat, which is when the offspring will be homozygous to the M gene.
