A new RFLP in intron 1 of the human c-Ha-ras1 gene and its close relationship with the variable tandem repeats in the region 3' to the gene.

Based on restriction fragment length polymorphism (RFLP) analysis of BamHI or MspI fragments, the human c-Ha-ras1 alleles could be divided into two major groups, one having about 80 copies of a 28 base pair (bp) sequence in the variable tandem repeat (VTR) region 1.4-kilobase pairs (kb) downstream from the end of the coding exon and the other having 40 copies of the sequence. We found a second RFLP in intron 1 of the c-Ha-ras1 gene at a position about 80 bp upstream from the 5'-end of exon 1. The size of the PstI fragments carrying this region is either 371 or 359 bp depending on the numbers of a hexanucleotide sequence, GGGCCT. In larger fragments, the unit sequence was repeated four times, while in smaller fragments it was repeated twice. Unexpectedly, we found that the alleles with 80 copies of the 28 bp sequence in the VTR region all carried two repeats of GGGCCT in intron 1, while alleles with 40 copies all had four repeats of the GGGCCT sequence.