一个新的泥鳅雄性特异DNA片段（简报）

世界上现存鱼类多达24000余种．是脊椎动物中分布最广，种类最多的类群．具有多种多样的生物学特性和重大的经济价值。与高等脊椎动物相比．其性别决定具有多样性和可塑性。大多数鱼类的性别决定机制很原始。性染色体的分化处于萌芽状态。在已进行细胞遗传学研究的1700多种鱼类中．大约有176种（占10．4％）发现有明显的异型性染色体。

IDENTIFICATION OF A NOVEL MALE-SPECIFIC DNA MARKER IN LOACH (Misgurnus anguillicaudatus)

The loach is widely distributed in China and cultivated enormously with the price increased in recent years. Its sex determination type and sex chromosome has not been recognized. In the present study, we report a novel sex-specific DNA marker in loach Misgurnus anguillicaudatus. The animals used in our experiments were collected from a wild population in wetland on the ancient Yellow river, Yanjin Country, Henan Province. 220 random primers were used for random amplified polymorphic DNA-polymerase chain reaction （RAPD-PCR） with the genomie DNA from two sex individuals as template. When using the S2111 primer, a novel 1 040bp sex-specific PCR product was amplified from known male fish. This fragment of DNA was cloned and sequenced. Two primers （MAmfl-P1 and -P2） were designed from the cloned sex-specic sequence to amplify the male-specific fragment using PCR for sexing, with the house-keeping gene β-actin as positive control. Sex-specific bands in the gel were represented in the males but none were found in the females. The PCR products in the gel were then transferred onto nylon membranes and hybridized with a DIG-labeled probe of the cloned male-specific DNA fragment. Clear hybridization signals were found only in the male loach. The same result was obtained from dot blotting hybridization. The fragment is a repetitive DNA, and presents its closely related species Paramisgurnus dabryanus but not linked to sex. The cloning of the male-specific DNA laid a good foundation for the isolation of gender-specific chromosome segments with chromosomal walking or gene library, and improved the mechanism exploration of sex chromosome evolution in fish.