| Isozyme and Random Amplified Polymorphic DNA (RAPD) were employed to investigate the genetic diversity and genetic differentiation of wild and gynogencsis population in Paralichthys olivaceu. DNA samples of parent and filial generation of gynogenesis were comparatively analyzed by RAPD. The homologous fragment of SRY gene from flounder genome was PCR amplified and sequenced. Some sex-linkage bands in RAPD amplification were cloned into bacteria vector and sequenced. 1. Two isozyme loci, Ldh-C and Cat, were found to be recombined in their chromosomes in the gynogenesis population of Paralichthys olivaceu. The recombination rates between isozyme locus and centromere were 52.6% and 29.8% respectively. The high recombination rates may be related to the small size of fish chromosome arms. Total 22 out of 136 DNA bands amplified by RAPD were found segregation in gynogenesis. However, whether these bands caused by recombination were hard to perorate owing to the analysis method restriction. 2. Isozyme mean proportion of polymorphic loci (P) and the average heterozygosities (H) of gynogenesis population in Paralichthys ohvaceu were 6.90% and 0.03 50 respectively. In order to obtain correct results we developed a modified arithmetic of genetic diversity of RAPD. P and H of wild population by RAPD were 20.88% and 0.0852, proportion of polymorphic bands was 37.57%; P and H of gynogenesis population by RAPD were 8.98% and 0.03 898, proportion of polymorphic bands was 16.18%. Results from RAPD and isozymc analyses were shown to be accorded. 3. Genetic similarity and genetic distance between wild and gynogenesis population were 0.9036 and 0.10 14, respectively. Genetic distance was higher than average level between geographical populations of fish. The index of genetic diversity of gynogenesls vi population (H0 =7.1982) was lower than that of wild population (R. =28.0986) Genetic differentiation between gynogenesis and wild population, H,,O,/H. = 0.97 16, (H-H~) IHsp = 0.0284, showing 97.16% distributed within populations and only 2.84% between populations. 4. All parameters, including mean proportion of polymorphic loci (P) and the average heterozygosities (H) of isozyme; P and H as well as proportion of polymorphic bands of RAPD; index of genetic diversity (H0), indicated the genetic diversity of gynogenesis population badly lose comparing with that of wild population. The proportions of reduction were 55.390/c - 77.74%. 5. DNA samples of parent and filial generation of gynogenesis were comparatively analyzed by RAPD. Those DNA bands expressed in female parent but not in male parent also expressed in gynogenesis filial; DNA bands expressed in male parent but not in female parent didn抰 express in gynonensis, while normally expressed in dcploid control fish. Germ plasm of sperm had been destroyed thoroughly by UV radiation, all germ plasm of gynogenesis filial were from female parent. 6. To detect sex determination mechanism of Paralichthys olivaceu, the homologous fragment of SRY gene was PCR amplified and sequenced. PCR amplification had no difference between individual and sex. A 648bp fragment from Paralichihys olivaceu, named sry-2, was sequenced and only had 35% homologous compared with human SRY. Four out of 1533 RAPD amplification DNA bands were found to be sex linkage. These bands were then cloned into bacteria vector and sequen...
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