Genetic disorders of sheep in New Zealand: a review and perspective.

Genetic disorders of sheep that have occurred in New Zealand are reviewed and discussed with regard to phenotype, inheritance and, where known, genotype. Inbreeding was a major factor in the emergence of some of them. The various disorders reflect a continuum, ranging from simple monogenic diseases or malformations due to dysfunctional gene products, those monogenic disorders dependant on environmental interactions, malformations due to homeotic gene dysfunctions, and multifactorial diseases for which genetic factors are associated with disease susceptibility. Chromosomal aberrations, although of limited importance, have contributed to an understanding of the physical chromosome map and derivative linkage map of sheep.