Studies On The Population Genetic Structure And Phylogeny Of Chicken MHC-B-F Gene Exon 2,3

MHC (Major histocompatibility complex) is composed by a group of genes of close interconnected highly-density and viable coding major histocompatibility antigens. They are mainly distributed in a certain area of a certain chromosome of vertebrates. They are a multi-gene family related to immunity and anti-diseases. Right now there are some researches showing that chicken's genes mostly determine its ability of anti-MDV. And the gene group of MHC has a close relationship with anti-MDV. Especially the viability of MHC-B-F has even more influence to chicken's ability of anti-MDV.This research has sequenced the exon2,3 ofMHC-B-F gene for 4 breeds of chicken (AA, A03, E₁, Huxu chickens)and determined 3 variation sites. The results shows as following:MHC-B-F exon 2 is 264bp long. The content of T+A is 36.6% and G+C is 63.5%, respectively. The content of G+C is higher than T+A. 50 variation sites have been detected, which are about 18.94% of the analyzed spots. Among them there are 18 single polymorphism spots, which are about 6.82%. There are 32 simple information spots, which are around 12.12%. Polymorphism types have more upside down forms. Among the 44 individuals there are 39 haplotyles. Average haplotype have more varieties, around 0.988±0.010. Average nucleotide polymorphism is 9.795. Nucleotide variety rate is 3.710%. The heredity difference between the 4 chicken breeds is 0.03081-0.06388. Among them the heredity difference between E₁ chicken and A03 chicken is the least (0.03081). The heredity difference between Huxu chicken and A03 chicken is the most 0.06388. Except Phe and Gin, among 88 AA of exon 2 the difference of other 18 common AA content is obvious. Among them the Thr content is the richest, around 17% and has 28 amino variation sites。Exon 3 area is 273bp long. T+A content are 43.1%. G+C content is 56.8%. G+C content is higher than T+A content. 49 variation sites have been detected, around 17.95% of the analyzed spots. Among them there are 16 single polymorphism sports around 5.86%. There are 33 simple information spots, around 12.09%. The number of turning times is higher than that of the exchanging times. In the transition types, A/G is the main type. In the transversion types, A/T is the main type. Among 47 individuals there are 45 haplotype. The variety rate of average haplotype is high, around 0.998±0.005. The average difference of nucleotide is 10.924. The variety rate of nucleotide is 4.002%. The heredity difference of the 4 chicken breeds is between 0.03404-0.05435. Among them the heredity difference of C chicken and H chicken is the least (0.03404). The heredity difference of H chicken and D chicken is the most (0.05435). Except His, among the 91 AA of exon2 coding the content difference of the other 19 common AA is a little big. Among them the Arg content is the richest, around 14.55%. There are 25 amino variation sites. All above indicates that the arrangement of exon2, 3 of chicken MHC-B-F shows a lot of varieties. The variety of the arrangement mostly shows in AA.Group analysis found out that there are 2 heredity sourses of MHC-B-F gene exon2,3. And those 2 sourses can be found in different species and groups.