Chromosome architecture of desi pigs of Kerala

Abstract

A cytogenetic analysis of the chromosomes of black desi pigs of Kerala was carried out. Fifty four black desi pigs housed at the AICRP on pigs: centre for Pig Production and Research, Mannuthy formed the material for study. Forty five Large White Yorkshire pigs were also studied for comparison of the chromosome architecture. Metaphase spreads were obtained by peripheral blood leukocyte culture in RPMI 1640 medium. A combination of pokeweed nitrogen and phytohemagglutinin was used for initiating mitosis. The metaphase spreads were G-banded by incubating them in 2 x SSC containing trypsin solution for 45 minutes at 60°C. The number, morphology and morphometric measurements of chromosomes were studied. The distinct visible bands observed in G-banding was compared to that of the standard G-banded karyotype of pigs. The karyotype revealed in desi pigs a chromosome diploid number of 38 (2n = 19). This consist of six pairs of submetacentric chromosomes, four pairs of metacentric chromosomes, six pairs of acrocentric chromosomes and a pair of sex chromosomes, either XX or XY. The X-chromosome was submetacentric and Y-chromosome metacentric. In Large White Yorkshire pigs included in the present study also the diploid number of chromosomes is 38, with similar morphological characteristics for the chromosomes as that of the desi pigs. Thus in morphology and number of chromosomes, the desi pigs maintained a similarity to that of large White Yorkshire pigs. The relative length of the largest chromosome which was a submetacentric one in both breeds was 11.69 ± 0.19 in desi pigs and 11.35 ± 0.37 in large White Yorkshire pigs. The Y-chromosome was the smallest chromosome in desi and large White Yorkshire pigs. The Y-chromosome had a relative length of 1.95 ± 0.12 in desi pigs and 1.7 ± 0.07 in large White Yorkshire pigs. The relative length of X-chromosome of desi and large White Yorkshire pigs were 4.63 ± 0.25 and 5.01 ± 0.22 respectively. The arm ratio of the submetacentric chromosomes was highest for chromosome 2 in both the breeds. The arm ratio was lowest for chromosome 8 in desi pigs and chromosome 5 in large White Yorkshire pigs. The ann ratio of the X-chromosome was 1.97 ± 0.08 for desi pigs and 1.81 ± 0.15 for the large White Yorkshire pigs. The centromeric index measurements varied from 23.06 ± 0.84 to 42.68 ± 0.71 for desi pigs and 26.2 ± 0.89 to 39.45 ± 1.51 for large White , Yorkshire pigs. The centromeric index value was highest for chromosome 8 and lowest for chromosome 2 in both breeds. The X-chromosome had a Centromeric Index of 32.09 ± 1.17 in desi pigs and 36.33 ± 1.64 in large White Yorkshire pigs. The bands obtained by G-banding of the chromosomes of desi pigs were comparable to the standard G-banded karyotype of pigs.