Direct microscopic detection of a specific DNA sequence eg, FISH;
Family associations by linkage analysis using DNA polymorphisms;
Analysis of the DNA or RNA sequences and mutation detection (usually by PCR).
The sequence may be identified by determination of the size of the DNA fragment after digestion with a restriction endonuclease and/or binding of a non-specific fluorescent probe or a specific DNA probe labelled with a detection system eg, radio-isotopic, chemiluminescent, fluorescent or enzymatic detection methods.
If a number of mutations can give rise to the genetic disease in question, nucleotide sequencing or linkage analysis may be necessary.
The sequence targeted for identification may be the normal sequence, a polymorphism, or a disease-causing mutation.
Deletions, duplications or variable repeat sequences can also be targeted.
Testing is performed in relatively few laboratories so specimens may have to be referred.
The pathologist should be consulted prior to organising specimen collection.