What is the method used for clinical testing of Fragile X syndrome?

The method used for clinical testing of Fragile X syndrome is Southern blot and PCR because this approach allows for the detection of the CGG repeat expansion in the FMR1 gene, which is responsible for the condition. Fragile X syndrome is characterized by having an abnormally high number of CGG repeats, which can be identified through these molecular techniques. Southern blot is particularly useful for analyzing the size of the repeats, while PCR amplification allows for the quantification of the repeats, providing insight into whether an individual is a carrier or affected by the syndrome.

Other methods listed, such as ELISA, are primarily used for detecting proteins rather than genetic material, which makes them unsuitable for diagnosing a genetic condition like Fragile X. Western blot is aimed at protein analysis and doesn't assess nucleic acid alterations. Fluorescent in situ hybridization (FISH), although a powerful technique for visualizing specific DNA sequences within chromosomes, is not the preferred method for assessing the repeat expansions relevant to Fragile X syndrome, where quantification is crucial. Thus, the combination of Southern blot and PCR is specifically tailored to uncover the genetic underpinnings of Fragile X syndrome.