Comparison of chromosomal architecture of Sahiwal and crossbred Sahiwal cattle

The karyological investigation using 16 purebred Sahiwal and 16 Jersey X Sahiwal cattle (8 males and 8 females of each genetic group) revealed the diploid chromosome number to be 60. All the 29 pairs of autosomes were acrocentric, while the X-chromosome was sub-metacentric in both the genetic groups. Acrocentric Y chromosome of Sahiwal differed from small submetacentric chromosome of Jersey X Sahiwal cattle in its morphology. The relative length of autosomes ranged from 1.74 ± 0.01 to 5.28 ± 0.02 in Sahiwal and from 1.72 ± 0.01 to 5.26 ± 0.02 in Jersey X Sahiwal crosses. X-Chromosome was the second largest chromosome in both the genetic groups. The contribution of X and Y chromosomes to the total genome were 5.07 and 1.99 per cent to the total genome in Sahiwal and 5.06 and 2.20 per cent in Jersey X Sahiwal cattle, respectively. The arm ratio, centromeric index and morphological index for the X-chromosome of Sahiwal and Jersey X Sahiwal cattle were 1.89, 0.35, 2.87 and 1.84, 0.36, 2.76, respectively. The arm ratio, centromeric index and morphological index for the Y-chromosome of Jersey X Sahiwal cattle were 1.63, 0.35 and 1.41, respectively.