Silent APC (adenomatous polyposis coli) gene polymorphism in the Portuguese population.

We describe a new, silent polymorphism in exon 15 of the APC gene on chromosome 5q in the Portuguese population. The polymorphism is located at codon 1442 and results in a CCT-->CCA (Pro) base transversion, with no amino acid change. Population analysis in unrelated healthy controls indicated that the polymorphism was present in 2 out of 50 individuals giving an allele frequency of 0.02 +/- 0.01. The polymorphism is the most common encountered in the Portuguese population in the mutation cluster region of exon 15, and has not been previously described in other populations.