THE USE OF DNA MARKERS IN THE PRECLINICAL DIAGNOSIS OF FAMILIAL ADENOMATOUS POLYPOSIS IN FAMILIES IN SOUTH-AFRICA

Haplotype association studies were performed in 10 unrelated South Afr ican families and 1 German immigrant family with familial adenomatous polyposis (FAP). Three DNA probes, recognising five restriction fragme nt length polymorphisms (RFLPs) around the gene locus for FAP on chrom osome 5q, were used. The RFLP analysis was informative or partially in formative in all the families studied. Five haplotypes were found to s egregate with the disease locus. The predominant association of two of these haplotypes with FAP in the South African families suggests that two mutations may cause the disease in about 70% of families in this population. Meiotic recombination events were detected between the FAP gene and probe M4 (D5S6), but not probes Pi227 (D5S37) and C11p11 (D5 S71), Haplotype analysis allowed the preclinical diagnosis of FAP in 5 subjects.