RESUMEN
Background: Molecular genetic analysis is the only method that allows accurate detection of Cystic Fibrosis (CF) carriers. Nevertheless, its application is restricted to those families in which the affected child holds known mutations. Since most Chilean CF patients already studied are heterozygous and carry a mutation not yet characterized, direct identification of carriers is limited. Linkage analysis of Restriction Fragment Length Polymorphisms (RFLP), using DNA markers closely linked to the CFTR gene, is a useful tool for the detection of carriers in families in which the patient carries an unknown mutation. Aim: To emphasize the usefulness of KM19 and MetH markers for RFLP analysis in extended genealogies in order to identify carriers of unknown mutations. Material and Methods: Selection of three families, in which a sibling of an index case, identified as ÐF-508/unknown mutation, could not be identified as heterozygous carrier or a normal homozygous. Haplotypic characterization for KM19 and MetH markers was performed by PCR amplification of genomic DNA followed by allele specific restriction enzymatic digestion. Results: The siblings of two families were identified as carriers and the sibling of the third family was identified as normal. Conclusions: KM19 and MetH haplotypic analysis provided a rapid method for carrier detection in the families under study. The analysis may be used as a supplement to direct genetic diagnosis and be helpful in genetic counseling.