Abstract

A subclass of human tandemly repeated DNA contains very short simple sequence repeats such as (dC-dA). (dG-dT), designated as CA repeats or (CA). It is now recognized that there are 50,000-100,000 interspaced (CA), blocks in the human genome. The function of these repeat sequences remains obscure, but since (CA). exhibit high degree of length polymorphisms and Mendelian inheritance, they can be extremely useful for genetic diagnosis of hereditary diseases. In this paper, we have examined the CA repeat polymorphism at the D5S346 locus, which is located 30~70kb downstream to the APC (adenomatous polyposis coli) gene responsible for development of familial adenomatous polyposis, in 55 unrelated Koreans. We were able to identify 11 different alleles ranging from 114 to 138 base pairs(bp) in size. The observed heterozygosity was 0.60. Using this information, we could successfully make presymptomatic diagnosis of all the at-risk individuals in 2 Korean familial adenomatous polyposis(FAP) families. Our result indicates that higly polymorphic dinucleotide (CA)-repeat marker D5S346 can serve as an important tool for presymptomatic diagnosis of Korean FAP families.

• Keywords: CA-repeat polymorphism, APC gene, Familial adenomatous polyposis, Link-age analysis