Studies On The Structure And Genetic Characteristics Of Complete Mitochondrial Genomes And 5S RDNA In Topmouth Culter(TC♀) ×Blunt Snout Bream(BSB♂) Hybrids

Mitochondria act as cellular energy suppliers in eukaryotic cells,and they have their unique genetic system. mitochondrial DNA(mtDNA) is a small,diverse and self-replicating genome,which fits in the studies of molecular phylogenetic evolution,origin and speciation of species.5S rDNA is a kind of highly conserved tandem repeat sequences in eukaryotic cells,which is very important to life functions.Its NTS polymorphism is suitable molecular mark to study the evolution of species,population differentiation and genetic diversity.We obtained and analyzed the complete mitochondrial genomes of topmouth culter(TC♀) ×blunt snout bream(BSB♂) strain.In addition,we also obtained the 5S rDNA sequences of TB strain and its original parents. The major results in this paper were presented as follows:1.We firstly reported the genetic information of the complete mitochondrial genomes in TB F1,F2 and F3. The complete mitochondrial DNA(mtDNA) sequences of TB F1,F2 and F3 are 16619 bp,16620bp and 16620 bp in length,respectively.It is different in length among generations,we speculated that it is caused by polymorphism between population.And it’s also shorter than the complete mtDNA sequence of original female parent TC(16622bp) in length,we speculated that it is caused during the process of distant hybridization.Compared with its original parents,we found that TB strain is more similar to its original female parent TC in the complete mitochondrial genomes.The study confirms the complete mitochondrial genomes of hybrids still followed strict maternal inheritance.2.We analysised the complete mitochondrial genomes of TB strain.Similar to other vertebrates, the complete mitochondrial genomes encoded the 37 genes consisting of 2 non-coding region(a control region and a OL), 2 rRNA genes, 22 tRNA genes and 13 protein-coding genes. The characters of gene organization and the molecular structure of the mt DNA genomes in TB strain were described in detail,including three conserved domains of control regions.In the meanwhile,we built NJ phylogenetic tree based on the mtDNA genome of TB strain,its original parents and other 8 cyprinidae fish,with 2 other fish as outgroup.which confirmed that TB stain followed strict maternal inheritance,and showed TB strain was the product of distant hybridization from the side.3.The structure and variation of 5S rDNA in TB strain and its original parents were analysised.We found that there were 2 types of monomeric 5S rDNA classes in TC(designated class Ⅰ: 188bp; class Ⅱ: 286bp),while there was only 1 type in TB strain and BSB(designated class Ⅰ: 188bp).We speculated that TB strain lost one type of monomeric 5S rDNA class in TC during the process of distant hybridization.We also found dimeric 5S rDNA tandem arrays in TB strain(376bp and 564bp).Compared 376 bp 5S rDNA in TB strain and BSB,we found 7 nucleotide variations,6 nucleotide variations were among TB F1,F2 and F3,we speculated that TB strain had polymorphism as a group.