Abstract :
The aim of the present study was to assess the presence of single nucleotide polymorphisms
(SNPs) in the Growth Differentiating Factor 9 (GDF9) and Bone Morphogenetic Protein 15
(BMP15) genes, in two Greek sheep breeds i.e. Chios and Karagouniki, with high and moderate
litter size (LS) i.e. number of lambs born, respectively. An examination of association(s)
between the polymorphisms and LS, within breeds, was also conducted. Blood samples
from 92 Chios and 96 Karagouniki ewes were collected, while repeated records on LS, were
also available (n = 239 and 259, respectively). Detection of SNPs was performed on the DNA
products by PCR-RLFP analysis. Data analysis included examination of allelic and genotypic
differentiation between the breeds, testing for Hardy–Weinberg Equilibrium (HWE) and
association analysis between polymorphisms and LS. Genetic analysis showed that the G1
and G8 mutations of the GDF9 gene were significantly over-presented only in the highly
prolific breed (Chios). The B4 mutation of the BMP15 gene was significantly over-presented
only in the low prolific breed (Karagouniki). Both breeds were in Hardy–Weinberg disequilibrium
(HWD), possibly due to selection pressure, population sub-structure and genetic
drift. Certain polymorphisms of the G1, G4 and G8 sites of the GDF9 gene in the Chios breed
were found to show heterozygote advantage with no evidence of infertility for the homozygous
females. A similar trend was observed in the BMP15 gene although at no statistically
significant level. In the Karagouniki breed, no significant associations between the studied
polymorphisms and LS were detected.
