RESUMO
Achondroplasia is the most common form of dwarfism and has an incidence of approximately 1/7,500. In more than 97% of cases, it is caused by a recurrent point mutation, a G to A substitution at nucleotide position 1138 (G1138A) of the fibroblast growth factor receptor 3 gene. Although this is an autosomal dominant condition, more than 90% of all mutations occur sporadically making this one of the most mutagenic sites in the human genome. The reasons for the high spontaneous G1138A mutation rate are not known. This investigation was performed by developing a simple and rapid semi-quantitative allele specific PCR based assay capable of reliably detecting more than 25 mutant G1138A copies in a pool of 300,000 wild type molecules. Using this assay, the G1138A mutation frequency was measured in cell lines deficient in mismatch repair (LoVo, SW48) and comparing it with controls. No differences were found in the frequency of this point mutation between the mismatch repair deficient and wild type cell lines.