A new skeletal defect in sheep.

INTRODUCTION Inherited diseases in production animals can cause both economic losses to the owner and (sometimes) animal suffering. Consequently, significant research effort is often expended in an attempt to elucidate the genetic cause of the disease, which may lead to a means by which animals carrying defective genes can be removed from the gene pool. The majority of simply inherited diseases show a recessive pattern of inheritance, although some genes show either dominant or overdominant modes of inheritance. In the past, test mating of potential nucleus males has been the only effective method of identifying carrier males. However, because of the expense and time delay, few breeders use test matings. A more practical action has been to cull both the sire and dam if known (and possibly near relatives) whenever an undesirable inherited condition arises. More recently, the development of molecular DNA techniques has led to the use of either DNA markers or gene probes as a means of removing heterozygous animals from the population.