Chromosome architecture of desi pigs of Kerala
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Date
2001
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Department of Animal Genetics and Breeding, College of Veterinary and Animal Sciences, Mannuthy
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.
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