Polymorphism and sequence analysis on exons of IGF-I gene in goats.
The insulin like growth factor Ⅰ(IGF-Ⅰ) gene was studied as a candidate gene for sexual precocity and high prolificacy in some goat(Capra hircus) breeds.Single nucleotide polymorphisms(SNPs) of all exons of IGF-Ⅰ gene were detected in sexual precocity and high prolificacy breed(Jining Grey goat) and sexual late-maturing and moderate fecundity breed(Boer goat) and sexual late-maturing and low fecundity breeds(Angora and Inner Mongolia Cashmere goats) by polymerase chain reaction-single strand conformation polymorphism(PCR-SSCP).No polymorphism was detected in the amplified region in the four goat breeds tested.DNA fragments amplified in this research were cloned into pGM-T vector.The positive clones were further identified by PCR.The nucleotide sequences of four exons in goat IGF-Ⅰ were spliced and the corresponding amino acid sequences were deduced.The comparison of the fragments of all four exons of Jining Grey goat IGF-Ⅰ gene with those of human,cattle,sheep,rat,mouse and chicken showed that the homologies of the nucleotide sequences and amino acid sequences of the fragments among these seven species were from 79.6% to 99.3% and from 77.8% to 99.4% respectively.No special variation was found in amino acid sequence of Jining Grey goat.The results indicated that the IGF-Ⅰ gene was highly conserved among mammals,and may not be a major gene that affects the sexual precocity and high prolificacy in Jining Grey goats.