Sdudies On Polymorphism Of IGF-I Gene And IGF-IR Gene In Yaks And Relationship Analysis With Growth And Development

Using IGF-I gene and IGF-IR gene as main effect candidate gene of growth and development traits in yaks,adopting PCR-SSCP to check the polymorphism of IGF-I gene and IGF-IR gene in 404 yaks including 5 plateau region groups( TianzhuYak, Gannan Yak, Qinghai gaoyuan Yak, Xinjiang yak and breeding spices Datong Yak ) ,the PCR products with polymorphism fragments were cloned and sequenced to detect single nucleotide polymorphism.The polymorphism of IGF-I and IGF-IR and the relationship between polymorphism and yak partial production traits were studied in order to find a molecular marker for yak growth and development,the results show that:(1) Firstly, the polymorphism of PCR-SSCP was found in the 1 intron of the yak insulin-like growth factor I,the result show that The polymorphism is controlled by a pare of allele A and B.Comparing the sequences by BioEdit , the reason caused the polymorphism is deficiency of C. The frequences of allele genes A(B) are 0.9028 (0.0972),0.9234(0.0766),0.8485(0.1515),0.7929(0.2071),0.9200(0.0800) in breeding spices Datong Yak Tianzhu Yak, Gannan Yak, Qinghai gaoyuan yak Xinjiang yak,respectively. The allele gene A is the superiority gene in the five breeds.(2) The polymorphism of PCR-SSCP was found in the 5th exon of the yak insulin-likegrowth factorI,the result show that:there is significant deviation in interspices genotype distribution.Three genotypes were detected including AA ,AB, BB in Datong yak , and there was only AA genotype in other groups which achieved to homozygotic stage. The cloning sequences show that: the loci was caused by T→C trasition and it caused the transformation of allele A and allele B.(3) The polymorphism of PCR-SSCP was found in the yak insulin-like growth factor receptor I,the result show that The polymorphism is controlled by a pare of allele A and B.Comparing the sequences by BioEdit , the reason caused the polymorphism is C→G trasition.The frequences of allele genes A(B) are 0.6458(0.3542),0.6802(0.3198),0.7475(0.2525),0.5571(0.4429),0.6100(0.3900) in breeding spices Datong Yak Tianzhu Yak, Gannan Yak, Qinghai gaoyuan Yak Xinjiang yak,respectively.(4) Chi square test of Hardy-Winberg law was detected among the defferent breeds in the IGF-I-P2,IGF-I-P5,IGF-IR-P6 mutation loci.The result show that Xinjiang yak was not fit for Hardy-Weinberg law (P<0.01). The heterozygosity(He),the effective allelic number(Ne) and the polymorphism information contents(PIC) were detected in derent breeds,the result show that PIC of Qinghai gaoyuanYak was midrange polymorphism and PIC TianzhuYak, Gannan Yak, Xinjiang yak and Datong Yak were low polymorphism in IGF-I-P2 mutation loci . PIC of Datong Yak was midrange polymorphism and PIC of TianzhuYak, Gannan Yak, Xinjiang yak and Qinghai gaoyuan Yak were low polymorphism in IGF-I-P5 mutation loci .In IGF-IR-P6 mutation loci, He, Ne was similar in the 5 groups,PIC was midrange polymorphism.(5)In Datong yaks population, three polymorphic loci which IGF-I-P2, IGF-I-P5 and IGF-IR-P6 were associated to the yak growth and development traits during 0, 6, 12, 18 month. The result showed that IGF-I-P2 loci had a positive relation with Weight and body length, and weiht,body length of individual with genotype AA was significantly higher than those with genotype BB, AB during 6 month.Individuals with genotype AA at IGF-I-P2 and IGF-IR-P6 genotype AA had significantly higher withers. And Individuals with genotype AA at IGF-IR-P6 had significantly higher body Height of 18 month.(6) This paper researched the heterosis and growth characteristic traits in the three populations which Datong yak,Tianzhu yak and Gannan yak. The result showed that the Datong yak compared with Tianzhu yak and Gannan yak, had significant heterosis on the traits of body weight and body length. Among these populations, Datong yak was best population on these traits.