Polymorphisms in GDF9 Gene and Its Relationship with Litter Size in Five Breeds of Black Goats

In this study, we investigated the relationship between the genetic polymorphism of growth differentiation factor 9 (GDF9) genes and the litter size in 384 individuals of five breeds of black goats. Four pairs of primers were designed to detect single nucleotide polymorphism of GDF9 gene in goats by PCR-SSCP. The least square was used to analyze the relation between different genotypes and the litter size. The results showed that the PCR products from primer pair 1 (P1) displayed polymorphisms in three genotypes (AA, AB and BB) in big foot (BF) and Jintang (JT) black goats. For primer pairs of P2, P3 and P4, there was no polymorphism. The sequencing results revealed that there was a single nucleotide mutation (A792?G) in exon 2 of GDF9 gene in BF and JT black goats, and this mutation resulted in an amino acid change: valine?isoleucine. In BF and JT black goats, the average litter size in the third parity was significantly higher in genotype AA than both genotypes of AB and BB while the average little size of genotype AB was higher than that of genotype BB in the same parity. GDF9 gene could be therefore considered as a candi-date gene for marker-assisted selection of litter size trait in goats.