[Progress in molecular genetic diagnosis]

The most frequent monogenically inherited disorders and an increasing number of rare monogenic disorders are already mapped, and the genetic defect leading to the disease was in part of the genes identified. Thus, detection of carriers of different disorders becomes possible by indirect or direct genotype analysis. The introduction of new analytical methods, e.g. polymerase chain reaction (PCR) and microsatellites permits a faster and safer diagnosis and in addition, a smaller amount of biological material is necessary. The identification of genes that are mutated in different inherited malignancies improves cancer prevention strategies in these families. A new class of gene defects--the "dynamic" mutations--consisting in the expansion of trinucleotid repeats within disease genes was identified in several disorders (e.g. fragile X-Syndrome, Huntington's disease, myotonic dystrophy); expanding trinucleotid repeats may explain some problems regarding the mode of inheritance and anticipation observed in these disorders, that were so far not understood. For studies of complex genetic disorders several new approaches were developed, however, so far they cannot be used for diagnostic purposes.