CHROMOSOMAL ABNORMALITIES SHEEP

Abstract

Successful and creative plant-breeding work in a stock-raising is based on the estimation of genetic potential of separate breeds, herds and individuals, that is impossible without thorough genetic- populations knowledge. Knowledge of features of caryotype gives an opportunity objectively to estimate the breeds of animals taking into account their population-cytogenetic features, that assists more complete idea about the evolution of breeds. However such important agricultural object, as a domestic sheep, remains cytogenetic poorly studied, especially in a population-cytogenetic aspect.In literature different breeds have small information about frequency and spectrum of the inherited anomalies and populations of sheep. Most chromosomal and genic anomalies of sheep in general not research, although for practice of plant-breeding work necessary knowledge of reasons of their appearance. Caryotype of sheep is presented by 54 chromosomes, from them 26 pairs of autsom and one pair of sexual chromosomes (ХХ or ХУ). Three pairs of large metacentric and 23 pairs of acrocentric chromosomes of different size enter in the complement of autsom. For sheep as well as for other animals characteristic chromosomal polymorphism as a numerical varying of chromosomes in caryotype (aneuploidi and poliploidi), morphological aberations and associations of separate chromosomes. Chromosomal anomalies of sheep are reason of forming of nonviable gamet, that results in death of embryos on the early stages, and, as a result, to the considerable economic losses in economies. The facts of chromosomal aberation educed for sheep testify to the necessity of cytogenetic control of tribal animals, especially rams, with the aim of exposure of animals-transmitters of undesirable changes in caryotype and exception of them from a plant-breeding process.