POLYMORPHISM AT VNTR LOCUS-3' TO THE APOLIPOPROTEIN-B GENE IN A TUNISIAN POPULATION - DIFFERENCE FROM OTHER ETHNIC-GROUPS

The Hypervariable Region (HVR) detected at the 3' end of the apolipopr otein B (Apo B) locus has been the subject of numerous studies. As for many VNTR (variable number of tandem repeat), this locus is highly po lymorphic and until now about 20 alleles have been described. The geno type distribution in all populations follows the Hardy-Weinberg predic tions. A bimodal pattern of allele frequency distribution is apparent in all Caucasoid populations. We have analyzed the frequencies of diff erent alleles in a Tunisian population (123 individuals) by the polyme rase chain reaction technique and compared our results to those obtain ed in several ethnic groups. It appears that the distributions of the allele frequencies are very different: for Caucasoid populations, ther e are two peaks of frequencies for alleles with 36 and 48 repeats, but alleles of intermediate lengths are more frequent. Hixson et al. [(19 93)Hum Genet 91:475-479] have shown a similar difference between black and white American populations. We found the same results in a black African group. Some of the repeat units of this HVR contain a Ssp I re striction site and digestion of the PCR products by this enzyme gives different patterns on gradient acrylamide gel [Desmarais et al., 1993, Nucleic Acids Res 21:2179-2184.] The DNA of African individuals (42) has been analyzed to discover the origin of this new allele. Prelimina ry results indicate that these particular alleles probably arose by in trogression from the African population into the Tunisian one. (C) 199 5 Wiley-Liss, Inc.