A study of the pleiotropic effects of the dominant gene N in the New Zealand Romney sheep : being a thesis presented for the degree of Doctor of Philosophy in the University of New Zealand, Massey Agricultural College
In dealing with problems of inheritance in domestic animals the emphasis tends to be placed on those factors which are of economic importance. Such factors are likely to be the result of many interacting and related causes, both genetic and environmental. This has resulted in the use of an approach based on the concepts of multifactorial and population genetics of Fisher, Wright and other workers. Using these concepts, the existence of certain genetic and phenotypic correlations can be shown and the results of certain selection policies predicted. However it is of considerable interest to know the mechanisms whereby these correlations arise. One such mechanism is pleiotropy, and it is proposed in this thesis to show how N-type Romney sheep (Dry and Fraser 1947) can, by a study of the pleiotropy of the gene N, be used to investigate the chain of events leading to various genetic and environmental correlations amongst fleece and body characters of the sheep. The first part of the thesis is concerned with preliminary investigations of the growth of the N-type sheep, which were initiated as part of a study of the carcass quality of lambs from these sheep. It was as a result of this study that the potentialities for the second year's work were realised. The second part is concerned with realising these potentialities in a study of the relationship of the body growth of the lamb and the development of the fleece.