Study On Polymorphism Of Candidate Gene With Some Productive Performance In Yaks From Five Different Regions

In this study,the objects were Xinjiang,Tianzhu white,Gannan,around Qinghai Lake and Datong yak that was the bred breed.The genetic polymorphism of candidate gene in yak,such as PRL,PRLR,GH,GHR and IGF-Ⅰ,was researched with PCR-SSCP and PCR-RFLP.The body size and body weight of yak were used as the index for growth and development. Relative allele frequency,polymorphicsm information content(PIC),heterozygosity and effective allele numbers of above yaks were analyzed.Relation between polymorphic loci observed and traints for growth and development was analyzed by least square method.Then possibility of effect of PRL,PRLR,GH,GHR and IGF-Ⅰon candidate gene for productive performance was researched.The results were as follows.1.On polymorphism IGF-Ⅰgene researched by PCR-SSCP(1) The polymorphism of PCR-SSCP on the 1^st intron in IGF-Ⅰgene of yak was discovered for the first time.By measuring the polymorphism of PCR-SSCP on the 1^st intron in IGF-Ⅰgene,the results indicated that this polymorphic locus was controlled by a pair of alleles,namely allele A and B.according to comparing sequence with BioEdit software,a single base,C,was delected in the 67 bp.So,the polymorphic locus appeared.The gene frequency of allele A or B in Xinjiang yak,Tianzhu white yak,Gannan yak,yak around Qinghai Lake and Datong yak was 0.9028(0.0972),0.9234(0.0766),0.8485(0.1515), 0.7929(0.2071) and 0.9200(0.0800) respectively.Allele A was the predominant allele in five yak populations.(2) By analyzing the polymorphism of PCR-SSCP on the fifth extron in IGF-Ⅰgene,the results indicated,the distribution of genotype was significant difference among breeds.In Datong yak,there were three genotypes,that was AA,BB and AB.While in other yaks,only AA,without AB and BB,its distribution was monomorphism without polymorphic loci.So, they were heterozygosity.By cloning and sequencing,the polymorphism on the locus was resulted from mutation of allele A to B,which T mutated C in the 202 bp.(3) Different genotype of 2 polymorphic loci on IGF-Ⅰgene and index for productive traits were tested significantly.The results showed,the body weight and body length with AA on the 1^st intron in IGF-Ⅰgene were significantly higher than that with AB and BB(P＜0.05).(4) By analyzing the genotype of 2 polymorphic loci on IGF-Ⅰgene and early growth of Datong yak,the results indicated that there was significant different(P＜0.05) in square mean of body height between AA individual(91.43) and BB individual(80.00) with IGF-Ⅰ(P5) at 18 months old.So,AA individual may be selected.(5) By comparing body size Datong yak,Gananan yak and Tianzhu white yak at the age of 6-month,the results showed,in regardless male or female yaks,the body weight of Datong yak was heaver than that of Gananan yak and Tianzhu white yak.The body length of Datong yak was obviously higher than that of Gananan yak and Tianzhu white yak.The heart girth of Datong yak was a little larger than that of Gananan yak and Tianzhu white yak.So,in respect of growth index,there was obvious advantage in Datong yak.2.On polymorphism of GH and GHR gene tresearched by PCR-SSCP and PCR-RFLP.(1) There was a mutation from T to C on the locus of GH3 in the 183 bp.In them,A was the predominant allele.By Hardy-Weinberg equilibrium testing in 5 yak breeds,there was not equilibrium in Tianzhu white yak,Gannan yak,yak around Qinghai Lake and Datong yak.3 yak breeds were analyzed through least square method,GH3 obviously affected the body weight.In them,as for the mean value calculated by least square method,AA maximum,AB next and BB minimum.In addition,GH3 obviously affected the body length,AA maximum, AB next and BB minimum.GH3 didn't affect the body height,heart girth and cannon circumference significantly.(2) There was a mutation from A to C on mutation locus of GH4 gene in the 64bp.A was the predominant allele.By Hardy-Weinberg equilibrium testing in 5 yak breeds,there was not equilibrium in Gannan yak.Through analyzing 5 yak breeds with least square method,the results indicated that GH3 didn't affect the body weight significantly.(3) By PCR-SSCP analyzing,there was not polymorphism on GH5 locus.(4) By PCR-RFLP analyzing,the primer GH-1R was used to multiply the gene in yak with PCR.1244bp production was obtained.This fragment was cut by restriction enzyme,such as AvaⅠ,HaeⅢ,HinfⅠ,PstⅠand SmaⅠ,there were anticipative restriction enzyme cutting side, while without polymorphism.SmaⅠdidn't have restriction enzyme cutting side.By sequencing and comparing,it was found that enzyme cutting side "CCC|GGG" at 878 locus on SmaⅠwas lost,so,there was not enzyme cutting side of SmaⅠ.in this experiment. The primer GH-2R was used to multiply the genome in yak with PCR.1037 bp DNA fragment was obtained.This fragment was cut by restriction enzyme,such as HaeⅢ,HinfⅠ, SmaⅠand PstⅠ.the results indicated that there were enzyme cutting sides on HinfⅠ,SmaⅠ and PstⅠ.by electrophoresis testing,it was found that the results were consistent with the anticipation.However,there was not restriction polymorphism.GH-2R was found that enzyme cutting side "CC|GG" at 75 locus was lost in restriction enzyme HaeⅢcutting side.3.Polymorphism of PRL,PRLR gene researched by PCR-SSCPAs for the second and third extrons in PRL receptor gene,there were AA,AB and BB genotype in Xinjiang yak,Tianzhu white yak,Gannan yak,yak around Qinghai Lake and Datong yak.A allele in PRLR-exon2 was the predominant allele in 5 yak populations. PRLR-exon2 gene frequency in Xinjiang yak,Tianzhu white yak,Gannan yak,yak around Qinghai Lake and Datong yak was above 0.500,the A gene frequency was 0.520,0.560,0.600, 0.580 and 0.640 respectively.The PIC was middle polymorphism,which had a certain genetic effect.Sequencing indicated that there ware a mutation in the second extron of PRLR gene,it was A to G in the 174bp,which resulted in locus mutation and polymorphism.As for PRLR-exon3 gene,there were AA,AB and BB genotype in Xinjiang yak,Tianzhu white yak, Gannan yak,yak around Qinghai Lake and Datong yak.B allele was the predominant allele. By analyzing PCR-SSCP production of PRLR-exon3 gene,the polymorphism resulted from the base C substituting G in the 98bp.A(B) allele frequency in Xinjiang yak,Tianzhu white yak,Gannan yak,yak around Qinghai Lake and Datong yak was 0.460(0.540),0.420(0.480), 0.500(0.500),0.460(0.540) and 0.450(0.550) respectively.In PRLR-exon3,the polymorphism in Tianzhu white yak was higher,the polymorphism in other yak was middle. The heritability was higher.Crossbreeding vigor was strong.