Study On Bone Morphogenetic Protein Receptor IB As A Candidate Gene For Prolificacy In Sheep

Bone Morphogenetic Protein Receptor-IB(BMPR-IB) lay on the sixth chromosomes in sheep.Scientists have found that there were two mutations in BMPR-IB:one was 746 locus, another was 1113 locus.The A was replaced by the G in Chromosome sequence in 746 and the result of mutation was that glutamine acid changed into Arginine.The C was replaced by the A in choromose sequence in 1113 locus.This mutation didn't lead to amino acid change in Sheep.The methods of PCR-SSCP and PCR-RFLP were established in this study.Based on the genetic polymorphism of BMPR-IB gene, we try to link these candidate genes with the high productivity of sheep,to further provide scientific evidence for the basic genetic research on the sheep high productivity.With the powerful PCR-SSCP and PCR-RFLP technique, we analyzed the polymorphism of BMPR-IB in four different sheep groups, such as Hu sheep, Charolais sheep, Texel sheep and Charolais-Hu sheep. There were 80 blood samples of Hu sheep, Charolais sheep had 30 blood samples, Texel sheep and Charolais-Hu sheep had 30,40 blood samples respectively.1.Fragments amplified by primer had only one genotype (BB) in Hu sheep, the genotype frequences of BB and the gene frequences of B were 1.00 respectively. Fragments amplified by primer had three genotypes(BB,B+,++) in Charolais-Hu sheep,the genotype frequences of BB,B+and++were 0.05,0.70,0.25 respectively, the gene frequences of B and+were 0.40 and 0.60.Fragments amplified by primer had only one genotype (++) in Charolais sheep and Texel sheep, the genotype frequences of++ and the gene frequences of+were 1.00 respectively.2.χ2 fitness test on fragments and productivity showed that:Hu sheep and Charolais-Hu sheep had extremely high significance with low reproductive breeds of Charolais sheep and Texel sheep (P<0.001).The gene type distributing between Hu sheep and Charolais-Hu sheep was aslo extremely high significance (P<0.001).The gene type distributing between Charolais sheep and Texel was not significance (P<0.05).3.For the sake of identificating the effection of BMPR-IB on the sheep litter size, we marked individually Hu sheep,Charolais sheep,Texel sheep and Charolais-Hu sheep, detected the genetype and recorded the litter size of every sheep,finding the average rambing rate of the sheep with genotypes BB and B+were 225.1% and 203.7% respectively.But the average rambing rate of the sheep with genotypes++were 120%. The test proved that the variation of the BMPR-IB had effected on the litter size indeed.4.The least squares mean(LSM) and standard error(SE) for litter size of different BMPR-IB genotypes in Charolais-Hu sheep proved:the average litter size between the genotypes BB,B+of the Charolais-Hu sheep and the genotypes++of the Charolais-Hu sheep was high significance (P<0.001).This result proved the homozygote and heterozygote of the BMPR-IB gene in sheep whose litter size related closely to this gene.5.This study found BMPR-IB gene were all homozygotes during the Hu sheep blood patterns,this might be related to their fecundity. Meanwhile, this result showed that Hu sheep who from Zhe Jiang Hu sheep field were not complex with other sheep varieties by breed conservating.6.Gene mensuration showed that the mutation of BMPR-IB lay on 746 locus.The "A" was replaced by the "G".