| Summary: | 碩士 === 國立海洋大學 === 水產養殖學系 === 89 === The catfish, Clarias fuscus, is an economical and local species in Taiwan. Its natural distribution was gradually sparsity. Little is known about the genetic backbroud of natural populations and the cultured stock. Specific highly polymorphic markers are required to assess the inbreeding level associated with aquaculture and gene pool of this species.
For the past 30 years, fish geneticists have been using protein electrophoresis (isozyme) as their primary tool to charaterize population-level genetic variation in various fish species. But the resolution of protein electrophoresis is not always adequate for detective differences between populations or individuals. In 1985, Alec Jeffreys reported the development of multilocus DNA fingerprint by southern blot-detection of hypervariable minisatellites or variable number of tandem repeat (VNTRs) loci. The technology of DNA fingerprinting found application to various forensic and scientific problems. DNA fingerprinting determined in fishes have proven valuable in aquaculture and fish management, for identification of stocks, in discreted breeding populations and for estimating constributions to stock mixture. Therefore, the variable population genetic data are necessary. The molecular genetic techniques, such as RAPD (Random Amplified Polymorphic DNA)、AFLP (Amplified Restriction Fragment Polymorphism) and Microsatellite DNA, have also been used, but in this study , we used RAPD and microsatellite DNA technique, research for estimating genetic variation and identification of species differentiation in catfish and their hybrid.
RAPD markers assays are based on the amplification by polymerase chain reaction (PCR) of random DNA segment using primer consisting of small inverted repeats of artitrary oligonucleotid sequences. We tested 200 RAPD primers from UBC (University of British Columbia) for their utility in identifying genetic polymorphism in catfish, C. fuscus. Of the 200 primers, 49 were good and medium quality RAPD profiles, but just only 16 primers had clean, stable and reproducible RAPD pattern. The RAPD marker of primer No.105、149、158、198、210、211、218、245 and 287 are difference between catfish and hybrids progeny (C. fuscus × C. batrachus). The overall polymorphism was low among catfisfh from natural and aquaculture. Our study present RAPD marker as useful genetic markers for identified species different in catfish and hybrid.
However, the newest molecular technique, microsatellites are consist of tandomly repeat short motif arrays of one to five nucleotide sequences, flanked by regions of unique DNA sequences have been shown to be highly polymorphism in eukaryotic genomes. Due to the relatively high polymorphism microsatellite loci may be used as markers in studies parentage, quantitation genetics and population genetics. (GT)n repeats prove to be highly abundant. We reported the isolation and characterization of 18 (GT)n-microsatellite DNA markers, the specific microsatellite DNA primers for catfish, C. fuscus, in order to characterized wild and domesticated population and to refer to gene pools.
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