Abstract

Direct DNA analysis of the fragile X mutation has become available with the isolation of DNA probes that detect the unstable DNA sequence containing the CGG repeat. We present the various alternatives of combinations of probes and enzymes that can be used for the diagnosis of fragile X syndrome. An overview is given of all the different available probes. A different protocol is presented for postnatal and prenatal diagnosis of fragile X syndrome. This includes Southern blot analysis as well as direct analysis of the CGG repeat by PCR amplification. We discuss the role of constitutional cytogenetic analysis in the diagnosis of mentally retarded subjects and cytogenetic analysis for the diagnosis of fragile X syndrome.