Heteromorphism of homologus chromosomes in pure and crossbred cattle

Abstract

In order to characterise the chromosomal heteromorphism among the homologues, a cytogenetic study was conducted on 7 genetic groups, viz. Holstein-Friesian (HF),Jersey (J), Gir (G), 1/2HF 1/2G (HG), 1/2J 1/2G (JG), 1/2HF 1/2J 1/4G (HJG) and 1/2J 1/2HF 1/4G (JHG) in chromosomes Nos 1, 2 and X-chromosome. The main relative length on the longer chromosome No.1 was 5.54% and that for its shorter homologue was 5.22%, the per cent increase (PI)was 6.21. The mean relative length of the longer chromosome No.2 was 4.95% and that for its shorter homologue was 4.78% and the PI was 3.56%. The mean relative length of the longer X-chromosomewas 5.26% while in it shorter homologue was 4.87% with a PI of 8.10%. A significant (p<0.01) difference was observed in size of the longer and the shorter homologues of all the 3 chromosomes for all the genetic groups. The size difference in the homologues might be a result of the differential condensation of the chromosomal arms during the colchicine treatment.