STUDY ON KERATIN INTERMEDIATE FILAMENT TYPE I AND GROWTH HORMONE GENE POLYMORPHISMS IN RELATION TO WOOL QUALITY AND GROWTH TRAITS IN PATANWADI, MARWARI AND DUMBA SHEEP 1646
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Date
2012-10
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JAU,JUNAGADH
Abstract
For the present study, 150 blood samples (50 from each
breed viz. Dumba, Patanwadi and Marwari) were collected
randomly from animals located at Sheep Breeding Farm. Morbi,
Gujarat. Isolation of genomic DNA was carried out. The quality of
DNA was estimated by agarose gel electrophoresis. The
amplification of Growth hormone gene and KRT gene was carried
out using appropriate primer pairs, optimized reaction mixtures
and PGR profile. The genotyping was done with the help of PGR
RFLP. The POPGENE software was used for estimating allelic and
genotype frequencies at different loci of the genes and to verify
Hardy-Weinberg equilibrium. Genetic identity and genetic
distances were measured by Nei's original measures amone
various breeds. ^
A. A781G locus. 144 sheep were heterozygous |AB| and 6
sheep were homosygous (AA) hu, no homozygous ,BB| ind.vidual.
were found among all the three breeds. At A1575G locus of
Growth hormone gene, all sheep were homozygous (CO) but no
homozygous (DD) as well as heterozygous (CD) individuals were
found in all the three populations.
All breeds exhibited clear predominance of the A allele, with
its frequency in samples from Marwari breed as 0.54 and 0.50 in
Patanwadi breed and 0.52 in Dumba breed. The frequency of
allele B in three population was 0.46, 0.5 and 0.48, respectively.
Two genotypes viz. AA and AB were observed during the study at
different loci for GH gene. The genotypic frequencies of AB were
greater than AA for all the three breeds. Overall genotype
frequency of AB genotype was greater (0.94) than AA genotype
(0.06). This suggests that heterozygous genotype was favoured for
body weight and growth in all the three breeds of sheep.
At locus KRT 1.2, studies revealed three genotypes viz MM
MN and NN with genotype frequencies of 0.74, 0.24 0.02- 0 54
0.42 85 0.04 and 0.64, 0.36 85 0.00 for Marwari, Patanwadi and
Dumba breeds, respectively. The overall genotypic frequencies at
KRT 1.2 locus for MM, MN and NN were 0.64, 0.34 and 0 02
respectively. The overall allele frequencies for allele M and allele N
were 0.81 and 0.19 respectively. In general, the frequency of allele
M was higher that of allele N in all three breeds. Three genotypes
viz. MM, MN and NN were observed in the study. In general, the
genotypic frequencies of MM were higher than MN and NN in all
the three breeds.
Diversity analysis revealed that Marwari and Dumba
breeds were genetically more related (genetic identity = O.9992
and genetic distance = 0.0008). The matrix obtained showed high
value of genetic identity between breeds for the growth hormone
loci thus, less genetic distance was found between these breeds
The observed heterozygosity was higher than expected
heterozygosity in all the three breeds. The mean values of
observed and expected heterozygosity for GH gene were 0.96 and
0.5009 respectively; while the same for KRT gene were 0 34 and
0.3088 respectively. HWE was tested using chi-square test. In
case of GH gene, all three breeds showed significant deviation
from HWE (PsO.Ol); while, for KRT locus 1.2, all three breeds were
in HWE (P>0.05). The average hetero^gosity for GH gene and KRT
locus 1.2 were 0.4987 and 0.3037.
Least squares analysis was carried out for physical traits
and wool quality traits.Least squares means for birth weight
(BWT), three month weight (3WT), six month weight (6WT), adult
body weight (ABW), were 3.18 kg, 9.22 kg, 11.70 kg, 27^07 kg
while least squares means for staple length , fibre diameter and
medullation 0/0 were 5.92 cm, 42.77 p and 76.37 o/„ respectively.
The breed of the sheep was a significant (PsO.Ol) source of
variation in all the traits. Growth hormone genotype had highly
significant effect (P<0.01) on birth weight, the higher birth weight
being observed in AB heterozygotes.
Greater frequencies of allele A and genotypes AB and AA
Showed that selection favouurreeda AA Aa homo^gotes and AB heterozygotes. The measures of Net's genetic identity and
genetic distance showed that Marwari and Dumba are
genetically more close among the three breeds, Chi-square test
for HWE with respect to GH gene showed that all three breeds
were away fmm HWE, Chi-square test tor HWE with respect,
KRT gene showed that all three breeds were in HWE, Effect o'f
breed was highly significant (^PsO.-Ouli)) oonn bbiirrft-hh ,we i•g hut, 3-month
weight, 6-month weight, adult body weight, staple length, fibre
diameter and medullation (%). Mean birth weight for genotype
AA and AB were significantly (PsO.Ol) different, individuals
with AB genotype being higher in birth weight than those with
homozygous AA genotype.
The important conclusion that emerges from the study is
that Dumba seems intermediate between Patanwadi and
Marwari breeds of sheep with respect to GH and KRT gene. The
OH A1575G locus was completed fixed for CO genotype. No
individuals with BB homozygous for locus A781G, CD
hetero^gous or DO homo^gous for locus A1575G were
detected in all the three sheep population under study.
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Keywords
ANIMAL GENETICS AND BREEDING