| The tandem repeat sequences including the microsatellite and minisatellite repeat sequences, belonged to high repetitive sequences, and distributed widely in the genomes of some prokaryotes and all eukaryotes. Generally speaking, the repeat unit size of microsatellites was from 1 to 6 bp, and 7 to greater than 200 bp for minisatellites. The objective of this paper lied in three aspects: firstly, to know the composition and distribution character of tandem repeats in the genome of Chinese shrimp Fenneropenaeus chinensis through analyzing parts of the genomic sequences obtained by random sequencing; secondly, to screen some polymorphism SSR markers; thirdly, to identify the individuals and parentages of F. chinensis using the above SSR markers. The more detailed contents and results were as follows: 1, For the first time, the distribution and frequencies of microsatellite and minisatellite repeat sequences were studied based on the sense of whole genome level. a total of 3888 microsatellites and 700 minisatellites were found from the 2597 000bp cumulative length random genomic sequences which was about 1.23‰ of the entire genome. The cumulative length of tandem repeats was 305 555bp, accounting for 11.72% of total sequence length, in which the cumulative length of microsatellites was 232 979 bp, accounting for 8.97% of total length. This proportion was greater than those of other organisms, such as human and mosquito, etc. The relative abundance of repeat sequences was similar to the frequency of the length of each repeat type. In microsatellite repeats, the dinucleotides were the most rich type, the following was trinucleotides, tetranucleotides, mononucleotides, hexanucleotides and pentanucleotides; the twelve-nucleotides was the most common type in minisatellite repeats. The dominant repeat classes were also different from each other in different repeat type, such as the A in mononucleotide repeat type, the AT in dinucleotides, and the AAT in trinucleotides, etc. However, the number of repeat sequences and repeat copy number found in pentanucleotide repeats were less than those of tetranucleotide repeats and hexanucleotide repeats. Furthermore, it was found that the classes and copy numbers of 7, 11, 13 etc. primer-number-composed repeats were significantly less than those of repeat types beside them. The phenomena may suggest the evolution relation between the microsatellite and minisatellite repeat sequences, i.e. many long size repeat units constituting of minisatellite repeats might come of repeat units of microsatellites, especially, the mononucleotide, dinucleotide and trinucleotide repeat types. The frequency distribution character of the dinucleotide repeats were centralized in a middle-leaning-left position(being similar to the normal distribution), and different notably from the other repeat types in which fewer sequences were seen with increasing copy number. 2, Twelve primer pairs with high amplified polymorphisms were screened from 1900 random clone sequences. The analyzed results to the core repeat types of microsatellite sites with high amplified polymorphism indicated that the polymorphism sites mostly belonged to dinucleotide repeat types, and the polymorphism information had some relativity to the copy numbers of the core repeat unites, but no significant relativity existed. 3, In order to efficiently use the microsatellite primer pairs, the multiplex PCR was established in F. chinensis firstly, and the multiplex PCR Genescan was further used to identify the individuals and parentages. Finally, based on the establishment of a diplex PCR and triplex PCR, the triplex PCR was successfully applied to identify two male shrimps mated with two females from four uncertain males, and exactly distinguished the off-springs among seven half-sibs, seventeen full-sibs, and the total thirty-two full-sibs respectively, and also orientate any off-springs to their corresponding parentages.
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