现在、牛有五十多种畸形、都受等位基因突变的影响。大多数畸形是隐性遗传。实际上,只有双亲是突变型等位基因生出的后代才表现畸形。在此情况下,双亲的外表虽然正常,但他们是杂合子致命或半致命因子的携带者。这些因子可在纯合子中存在并会引起各种畸形。例如;隐性的形状(短颚症)在双亲中是不表现的: Now, there are more than 50 deformities in cattle, all affected by allelic mutations. Most deformities are recessive. In fact, only offspring born of parents with mutant alleles behave abnormally. In this case, although the parents’ appearance is normal, they are carriers of the lethal or semi-lethal factor of heterozygosity. These factors can exist in homozygotes and cause various deformities. For example; recessive shapes (short jaws) are not represented in both parents: