The Study Of Karyotype And Sex-determining Gene In Imposex Thais Clavigera

In this paper, Thais clavigera of gastropoda was investigated at chromosomes and sex-determining gene as a typical imposex animal to show the differences between the female , male and imposex individuals. The sex-determining gene was specially studied to explain the sex determining and imposex mechanism on genetic and molecular level. The experiments applied the theoretical basis for deep research in sex-determining mechanism of gastropoda and the molecular mechanism of imposex due to TBT pollution. The research try to fill in the gaps in the field of sex-determining studying in mollusk, to provide the theoretical basis for discovering the real reasons of imposex , and to control the TBT pollution to marine environment effectively.Karyotypes of two species belonging to genera of Thais(Thais clavigera and Thais luteostoma) were studied and the difference of chromosomes between normal and imposex individuals were compared. The results showed the dipyoid chromosome number of the two species is 2n=24. The chromosomes from Thais clavigera consist of eleven pairs of metacentric and a pair of acrocentric one and that of Thais luteostoma' s includes ten pairs of metacentric, one pair of submetacentric and one pair of acrocentric of chromosome. The chromosome number from imposex individuals of Thais clavigera had not any difference but their morphorlogy appeared some abnormal compared with normal individuals.The samples of Thais clavigera including male, normal female and imposex individuals were choosed to study the sex-determining mechanism . Two pairs of primers from SRYgene-HMG box were used to amplify the genomic DNA of the three samples .A specific 240bp fragment was obtained in the male but not in the females. The fragment was cloned into the pUCm-T vector and the identified positive clone was sequenced. RT-PCR analysis was also used to get the same the result. The homological analysis showed that there were homologous sequences of human SRY gene and Soxll gene inwas also used to get the same the result. The homological analysis showed that there were homologous sequences of human SRY gene and Soxll gene in Thais clavigera . It suggests that SRY is conserved during evolution.Above all, the results indicated that there is no sex chromosome but sex determining gene in Thais clavigera. There is no difference in molecular level between normal female and imposex individuals. It inferred that imposex induced by organotin pollution does not show out on the DNA level.