Lethal mutation

This is a mutation that results in the demise of the organism affected. An example of such a mutation can be observed in Manx cats. Characterised by their lack of tails and longer hind legs, Manx cats carry a dominant allele (M^L) that severely affects spinal development. All Manx cats are heterozygotes; cats that are homozygote for the M^L allele do not survive because the allele is recessive lethal.