[Study on Ha-ras RFLPs in gastric carcinoma and normal tissue DNAs of Chinese individuals].

By using recombinant plasmid PHS-49 as a probe, BamHI restriction fragment length polymorphisms (RFLPs) was studied in tumour DNAs of 36 gastric carcinoma patients and normal tissue DNAs of 25 unaffected Chinese individuals. Ten alleles and eighteen genotypes for Ha-ras gene were found. Four "rare" restriction fragments of size less than 6 kilobase pairs (kb) are first reported for Ha-ras locus in present paper, we inferred that these alleles might be one of the characteristics of genetic polymorphisms in Chinese population. Moreover, the frequency of some "rare" alleles and genotypes occurred in gastric carcinoma samples is significantly higher than that occurred in normal individuals. The results of pedigree analysis for two patients showed that some heterozygotes carried three or four alleles. It suggested that there may be more than one copy of Ha-ras gene sequence existed in a chromosome. The possible causes of the phenomenon mentioned above were discussed.