Study On DNA Polymorphism And Genetic Relationship In Six Strains Of Carassius Auratus

Carassius auratus reproduces by gynogenesis mechanism, which is a transition phase of monosexual and bisexual procreation in vertebrate evolution. Many scientists are interested in evolution genetics, molecule taxonomy and procreation mechanism of Carassius auratus. In this study, population structures in six strains of Carassius auratus were analyzed by PCR-RFLP, microsatellite markers and sequencing techniques. The aim was to reveal genetic evolution relationship of the six strains and gynogenesis mechanism for breeding, breed identification and genetic analysis of Carassius auratus. 1. PCR-RFLP analysis of Cyt b gene of mitochondrial DNA Five endonucleases were used to analyse amplified products of Cyt b gene. The results showed that restriction fragment length polymorphisms of Cyt b gene between strains or within Carassius auratus Hongji and Carassius auratus Jinji strains were detected by two enzymes HinfI and MspI. The size of Cyt b gene of Carassius auratus was about 1 260 bp. Four composite haplotypes were found in the six fish strains. According to the porportion of restriction fragments shared, the genetic distances among the 6 populations were calculated and relationships among them were analysed. Genetic distance of between Yeji and Heilongjing, Gaobeiji and Pengzeji was 0 while that of between Yeji and Hongji was 0.00039.2. Microsatellite analysis in six strains Carassius auratus The results showed that there were 6 alleles in J1 locus, 9 alleles in J9 locus, 10 alleles in MFW1 locus, 8 alleles in MFW19 locus and 11 alleles in J62 locus. The number of average allele was 8.8. In the same locus, nearly identical banding patterns were observed among intrastrain individual, however, the six strains differed from each other in electrophoresic patterns. This indicated that each strain possess specific pattern. The electrophoresic pattern clearly indicated homogeneity in the same population, and heterogeneity among populations. The results of the genetic distances and cluster analysis showed that the genetic distance was minimal (0.0032) between Pengzeji and Gaobeiji, following between Hongji and Jinji; maximal (0.8227) between Jinji and Yeji. 3. Mitochondrial DNA D-loop polymorphism analyse in three Carassius auratus strainsSequence analysis was conducted using MEGA program. There were 40 aberrance loci in 438bp sequence length, which account for 9.13%. Base substitution was 20,4.56%, with transition more than transversion, the rest was 20 intervene /default, the proportion of base substitution and intervene/default was 1:1. According to cluster tree, the founding was that the genetic distances between Hongji and Jinji was the shorter, following was Pengzeji. The result was identical with that of microsatellite and PCR-RFLP.