The Application Of DNA Barcode Technology In Agricultural Animal Research

In recent years,with the increasing number of farm animals,the expansion of farming scales,the appearance of transgenic animals and the growth of experimental animals and animal derived products,how to carry out management and identification of animal species effectively becomes an urgent problem that needs to be solved,as accurate identification of species is the basis for us to understand,explore and protect species.DNA Barcoding is a taxonomy method based on molecular genetic markers,which has been developed rapidly in recent years and has attracted wide attention because of its rapidity,accuracy and efficiency.As a DNA barcode,the cytochrome c oxidase subunit I gene(COI)in mitochondrial DNA(mt DNA)has been applied to various biological research fields successfully,such as species identification of animals and biological polymorphism analysis,but identification of different varieties in the same species is still blank.This experiment verifies feasibility and advantages of mitochondrial COI gene and 16 S r RNA gene as DNA barcodes in identification of agricultural animal species and varieties through genetic analysis of COI gene sequences in 233 samples,including 4 agricultural animal species and 8 varieties and comparing it with genetic analysis of mitochondrial 16 S r RNA gene sequence of these samples to provide new ideas and methods for the identification of varieties.Genetic analysis shows that:1.Gene fragments amplified by universal primer COI are about 670 bp,by 16 S r RNA are about 570 bp.These lengths can fully meet the requirements of DNA Barcoding.In these 233 samples,there are 25 haplotypes and 159 polymorphic information loci in COI gene sequence analysis;16 haplotypes and 88 polymorphic information loci in the analysis of 16 S r RNA gene sequence.Therefore,COI gene sequence has larger polymorphism information.2.By analyzing base composition of COI gene and 16 S r RNA gene sequence in all samples,it shows that the mean contents of A+T is far greater than that of G+C(the average content of A+T is 54.4% at minimum in base content of COI gene in beef cattle)and base bias is significant,which is in line with the characteristics of mitochondrial DNA base composition.3.By establishing phylogenetic tree of COI gene and 16 S r RNA gene sequence in all samples,the structure shows that phylogenetic trees constructed by NJ method and ME method are basically the same,and the same species clusters into independent branches with clear position and relationship,presenting the same result as genetic distance analysis.This shows that as DNA barcodes,COI gene and 16 S r RNA gene can be used in identification of farm animal species.4.By analyzing COI gene and 16 S r RNA gene sequence in pigs,we find that some haplotypes in Duroc are identical with the only haplotype in Landrace,with zero genetic distance and completely overlapped phylogenetic tree structure,and haplotypes in both varieties have crossed in phylogenetic tree structure.Result of two cattle varieties is the same.This result shows that as DNA barcodes,COI gene and 16 S r RNA gene are difficult to identify farm animal varieties.5.By analyzing 16 S r RNA gene sequence in all samples through single nucleotide polymorphism(SNP),we can successfully distinguish Duroc,Landrace and Large White,miniature pigs,which provides new ideas and experimental basis for the identification of agricultural animal varieties.