Single Gene Abnormalities

Identifying single gene abnormalities:

1) Gene sequencing

Gene sequencing will identify point mutations and small deletions/insertions in single genes. Gene sequencing can be done by two methods:

• Sanger sequencing involving:

i) An amplification step usually undertaken by polymerase chain reaction (PCR);

ii) A sequencing step.

• Next generation sequencing (NGS) describing the parallel sequencing of multiple genes.

2) Dosage analysis

Multiplex Ligation-dependent Probe Amplification (MLPA) can be used to detect gene dosage abnormalities caused by exon deletions and duplications within single genes. In the investigation of single gene disorders, its use is complementary to gene sequencing approaches that can detect point mutations but not dosage abnormalities.

3) Triplet repeat expansions

Pathological expansion of trinucleotide repeats within certain genes causes a range of neurological and neuromuscular diseases, known collectively as triplet repeat disorders. For many years Southern blotting was the predominant technique for investigating triplet repeat expansions, however PCR-based techniques have now largely superseded Southern blotting. You will be introduced to both Southern blotting and these PCR-based techniques.