Study On The Candidate Genes For Fecundity In Mongolian Sheep Double-lambs Group

In this study we choose the BMPR-IB gene which control Booroola Merino sheep prolificacy trait and BMP15 gene which affect Invedal and Hanna awaits prolificacy trait as candidate gene of prolificacy function,designed to explore the relationship between the two candidate genes and lamb reproductive traits of Mongolian sheep,provide a scientific basis for carrying out the research of Mongolia sheep high fecundity genetics.(1) Taking the single-lamb Mongolian sheep group (18),multiple births type of Small Tail Han sheep (30) as contrast groups of double-lambs Mongolian sheep group(50), using the polymerase chain reaction-restriction fragment length polymorphis ( Restriction Fragment Polymorphisms, RFLPs)molecular marker technique analysis genetic polymer- phism of the BMPR-IB gene in the double-lamb Mongolian sheep group.The results showed that: The BMPR-IB gene FecB mutation was absent in double-lambs Mongolian sheep group and single-lamb Mongolian sheep group,so BMPR-IB gene isn't the major gene that impact high productivity of Mongolian; the mutation was detected in Small Tail Han sheep breed and found three kinds of genotypes, the homozygous mutant (BB),heterozy- gous (B+) and wild-type (++), the genotype frequencies were 0.100,0.733 and 0.167, associated with litter size analysis indicated that BB genotype ewes and B + genotype ewes average litter size was significant difference (p <0.01),so we can infer that BMPR-IB gene is the Major gene for high fecundity of multiple births of Small Tail Han Sheep. By the chi-sequare (X2 )test showed that the gene localed in Small Tail Han Sheep significant deviations from Hardy-Weinberg Equilibrium ( P <0.05).(2) FecXI site in the BMP15 gene was detected by PCR-RFLP .The result showed: FecXI site mutation was absent in the Mongolian sheep double-lambs group, the single- lamb Mongolian sheep group and the Small Tail Han group. That is, FecXI site in the BMP15 gene isn't the major gene for high fecundity that affect Mongolia sheep and Small Tail Han sheep.(3)Using the single nucleotide polymorphism PCR-SSCP (Single Nucleotide Polymorphisms, SNPs) technology for the B1 site in BMP15 gene polymorphism analysis,results showed that: the corresponding mutation 28-30bp(CTT deletion)existe in the three groups and found three genotypes.The genotype frequencies of the wild-type (+ +), heterozygous (B +) and homozygous mutant (BB) were 0.020, 0.940and 0.040 in the Mongolian sheep double-lambs group ; Just found tow genotypes in Mongolian sheep single-lamb group , the genotype frequencies were 0.722(++), 0.278(B+); 0.300(++), 0.667(B+)and 0.033(BB)in Small Tail Han Sheep. Mongolian sheep ewe group genotype B + and + + genotype ewes average litter size was significant difference (p <0.01), inferred the B1 mutation maybe is the major gene to control the high fecundity in Mongolian sheep double-lambs group ; Small Tail Han sheep genotype group ewes average litter size was not significant difference(p>0.05 ). By the X2 test showed that the Mongolian sheep double-lambs group significant deviations from Hardy-Weinberg equilibrium (P<0.01); the locus of Mongolian sheep single-lamb group and Small Tail Han Sheep in Hardy-Weinberg equilibrium (P> 0.05).(4)Using the single nucleotide polymorphism PCR-SSCP (Single Nucleotide Polymorphisms, SNPs) technology for the B4 site in BMP15 gene polymorphism analysis, results showed that: B4 1100bp site (T→G) mutationa was absent in the three groups.But we found A base deletin at1000bp, C base nsert at 1032bp .The three genotype frequencies were 0.220(++), 0.420(B+)and 0.360(BB)in Mongolian sheep double-lambs group; 1.000(++), 0.000(B+)and 0.000(BB)in Mongolian sheep single-lamb group; 0.800(++), 0.000(B+)and 0.200(BB) in Small Tail Han group. Associated with litter size analysis showed that the Mongolian sheep double- lambs ewe group genotype B + and + + genotype ewes average litter size difference highly significant (p <0.05); Small Tail Han sheep genotype group difference genotypes ewes average litter size was not significant . The X2 test showed that the locus of Mongolian sheep single-lamb group,Mongolian sheep single-lamb group and Small Tail Han Sheep all were in Hardy-Weinberg equilibrium (P> 0.05).