O cromossomo Y na raça Chianina no Brasil

There were studied the karyotypes of 95 purebred Chianina bulls, distributed among 19 cattle farms in five Brazilian states. The objective was to investigate the incidence of individuals carring an acrocentric Y chromosome, typical of Bos taurus indicus breeds, in view of speculations that Indian breeds might have contributed to the formation of Chianina. All individual showed the Bos taurus taurus Y chromosome. The centromeric index obtained was 43.91%, which allowed us to classify the centromere of this chromosome as medially located. There were also studied 29 purebred Chianina bulls with the objective of verifying the presence of intraracial polymorphism at the Y chromosome. The centromeric index and relative size of the Y chromosome were determined. The lenght of the X chromosome served as a basis for estimating the relative size of Y. Analysis of variance showed differences among bulls only in the relative size of Y, no differences being detected in the centromeric index. We conclude that this polymorphism indicates the Chianina breed may have received contributions from other breeds in the remote past, or it may also indicate the possibility of more recent crosses.