Study On Polymorphism Of Growth Differentiation Factor 9 Gene And Its Relationship With High Prolificacy In Small Tail Han Sheep

Growth differentiation factor 9 (GDF-9) gene is a growth factor secreted by oocytes in growthing ovarian follicles, which is essential for normal follicular development. Based on the genetic polymorphism of GDF-9 gene, we try to link this candidate gene with the high prolificacy of Small Tail Han sheep, to futher provide scientific evidence for the basic genetic reseach on the high productivity of Small Tail Han sheep.Applying the powerful PCR-SSCP technique to analyze the polymorphism of growth differentiation factor 9 gene, we divided our samples into two groups: one grorp is the blood sample of 130 Small Tail Han sheep with littering records, another group is the blood sample of four different sheep breeds without littering records (Hu sheep, Small Tail Han sheep, Suffolk and Dorset). The results were as follows: fragments amplified by two primers had two genotypes (AA and AB) in Small Tail Han sheep with littering records. In Hu sheep and Dorset, fragments amplified by two primers had two genotypes(AA and AB). In Suffolk, fragments amplified by primer 1 had three genotypes(AA, AB and BB). Fragments amplified by primer 2 had two genotypes(AA and BB), Mutant gene had not been detected in Small Tail Han sheep without littering records. Fragments amplified by two primers reached to significant level among fourdifferent sheep breeds(P<0.01). X2 fittness test showed that fragments amplified by two primers were in a state of Hardy-weinberg equilibrium.We cloned and sequenced fragments amplified by primer 1, which included one mutation locis. It showed that there was one mutation A-G in 152 bp of exon 1, and we translated this mutatal and nonnal sequences into amino acid. By running a popular analysis tool TFSEAKCH ver 1.3, we found mutation of nucleotide brought out a change in amino acid (N→D). Protein second structure prediction showed that mutation in amino acid changed second structure(coil-a-helix), and had difference in the following two amino acids, H, L from coil to a-helix.In Small Tail Han sheep with Uttering records, least squares analysis showed that fragments amplified by primer 1 had significant effects on the first parity (P<0.05), and had more significant effects on the second parity (P<0.01). Fragments amplified by primer 2 had no significant effects on the first and second parity. According to all of our results, we conclude that the polymorphism of fragments amplified by primer 1 probably associates with the reproductive performance of Small Tail Han sheep, but need further studies.