[Prenatal diagnosis. The era of molecular biology].

The advent of molecular genetic engineering has major implications in the diagnosis of genetic diseases by allowing a direct approach of the gene. The purpose of this article is to recall the techniques of molecular biology and to survey their potential and their applications which affect several fields of medical genetics: direct diagnosis of point mutations and deletions, indirect diagnosis by polymorphic linkage, indirect diagnosis of X linked recessive diseases (diagnosis of female carriers or recent mutations, prenatal diagnosis), autosomal recessive diseases (21 hydroxylase deficiency and cystic fibrosis) and autosomal dominant diseases, and finally diagnosis of sex and of chromosomal abnormalities.