SSR Analysis Of Cattle,Goat And Sheep And Study Of The Evolution Mechanism Of MHC

The genetic diversity is the breeding basis of domestic animal,while the polymorphism of DNA displays an important role in assessing population genetic diversity and population genetic structure.Base on high polymorphism of microsatellite marker(SSR),which resulting in this system utilized widely for estimation of genetic conservation during pasted more than twenty years.Up to date,amount of studies with this system indicated that the population structure of domestic animal following their management history and geographical distribution.In addition,the major histocompatibility complex(MHC)plays a key role in adaptive immunity of animal as common known.Due to the genetic diversity of MHC was closely related to animal disease resistance,it became to fresh and interesting genetic marker system in assessing domestic animal diversity,particular in indigenous or native ppulations.However,the mechanism of formation and maintenance in MHC diversity is not complete understanding until current time.In this study,1439 samples from 53 populations including goat(37 populations),sheep(11 populations)and cattle(5 populations)with different geographical distribution and management background were sampled.Then microsatellite markers(genome SSR)and MHC related microsatellite markers(MHC SSR)were used to analyze the genetic diversity of all populations respectively.What's more,through comparison of the diversity and population genetic structure between two levels(genome SSR,and MHC),to investigate the possible potential evolutionary principle of MHC,as well as provide the basic data for breeding of livestock with high disease resistance property in coming time.In summary,the main results and conclusions of this study are as follows:1.By analyzing the genetic diversity of goats,sheep and cattle with genome SSRs,which showed that the genetic relationship was consistent with their geographical distribution and management background.2.The BM1258 locus were highly polymorphic in three species by analyzing the genetic parameters of MHC related SSR locus(BM1258,BF1,DYMS1)in goat,sheep and cattle.The BF1 locus were medium polymorphic in the cattle and goat populations,highly polymorphism in the sheep populations;DYMS1 locus appeared low polymorphism in the goat and sheep populations,and non-polymorphism detected in the cattle populations.3.The six locus(INRA063,CSRD247,SPS113,OarFCB48,TGLA53,OarFCB20 and MAF70)shared by goat,sheep and cattle with high polymorphism.And the result inferred that these six locus can be used to analyze genetic diversity of cross-species research.4.By comparing the genetic parameters of the SSR locus and the MHC related SSR locus in the population,which revealed that the heterozygosity of the MHC-SSR was lower in the population than that of genomic SSR.Which deduced that the role of heterozygote advantage may be relatively weak to modified the polymorphism of MHC.5.According to the result of compared population relationship between SSR marker system and MHC-SSR marker system in those goat populations with different geographical location and commercial breeds indicated that MHC and immune-related genetic markers are more suitable for assessment adaptive evolution history,but the population migration,genetic diversity estiamtion,and population structure defined in the general sense,like that presented by the genomic SSR wih genetic drift.6.Through analyzing the genetic structure of goats,sheep and bovine species,cross-species polymorphism in MHC region was investigated,which indicates that MHC were effected by balance selection during evolution.7.The last but not least importance,the FST value of MHC-SSR level was higher than that in SSR level by analyzing the genetic differentiation among populations was identified.It implied that the rare allele of MHC region might be produced by the results of adaptive selection in MHC from environment and epidemic history.