[Diagnosis of familial adenomatous polyposis based on DNA]

Familial adenomatous polyposis is an autosomal dominant precancerous condition, characterized by the appearance of hundreds to thousands of colorectal polyps. Mutation of the APC gene located on 5q21-22 plays the major role in its etiology.

Diagnoses and genetic prognosis of 7 persons of a family with previous case of FAP using combination of two molecular methods-heteroduplex and linkage analysis.

In heteroduplex analysis (HDA) the E-G region of the 15 exon of the APC gene was amplified using PCR. PCR products were then loaded on nondenaturating polyacrylamid gele and visualised by silver staining. In linkage analysis we used linkage between pathologic alele of the APC gene and MspI polymorphism.

Using heteroduplex analysis an identical mutation in two persons in suspected region was detected and linkage analysis revealed that pathologic alele of APC gene in one person is linked to B2 alele of MspI polymorphism. For the second person the linkage analysis was not informative.

Using these methods presymptomatic diagnostics of FAP, genetic prognosis and detection of persons at high risk have become available. Comparing to classical diagnostics these methods are quick, exact not embarrassing for the patient and it is not necessary to repeat them. (Fig. 3, Ref. 13.)