ANALYSIS OF THE FIRST INTRON OF TNFB GENE BY NCOI RFLP IN KOREANS

The tumor necrosis factor B (TNFB) gene is closely liked with tumor ne crosis factor A (TNFA) gene between the HLA-B and C2 genes on chromoso me 6p21.3. Several genetic variabilities at the human TNFB loci have b een identified, which are the NcoI restriction fragment length polymor phism (RFLP) in the first intron, amino acid substitution at codon 26 of exon 3 and EcoRI RFLP in untranslated exon 4. The NcoI RFLP of TNFB gene gives two allelic fragments of 238/259 bp and 497 bp, correspond ing to TNFB1 and TNFB*2 alleles, respectively. To investigate the fre quency of NcoI RFLP in the first intron of TNFB in Koreans and to comp are to that of other ethnic population, genomic DNAs were extracted fr om leukocytes of 305 unrelated healthy Koreans and amplified the first intron of TNFB gene by PCR. The phenotype frequencies of NcoI RFLP su ch as TNFB1/TNFB*1, TNFB*1/TNFB*2 and TNFB*2/TNFB*2 were 8.6% (n = 26 ), 45.2% (n = 138) and 46.2% (n=141), respectively. The estimated alle le frequencies for TNFBI and TNFB*2 were 0.3115 and 0.6885, respectiv ely. The observed and expected frequencies were in good agreement with the Hardy-Weinberg's equilibrium. The heterozygosity revealed 45.2% a nd the allele frequencies of NcoI RFLP of TNFB in Koreans were observe d comparatively similar to those of other ethnic groups.