The reason to chose a particular molecular method can be influenced by disease detection, monitoring or therapy in certain patient populations.

Molecular methodologies can be used to identify alterations or variations or changes in DNA sequencing that can cause disease. Sequence alterations that are known to cause disease are termed mutations. These changes or mutations can be applied to areas of the clinical lab such as infectious disease, paternity, genetic testing, and pharmacogenetics.

Some of the more common alterations are:

Deletion: a missing nucleotide or other portion of DNA sequence

Insertion: an extra DNA nucleotide or other portion of DNA sequence

Missense: a nucleotide or sequence substitution that codes for a different amino acid

Nonsense: a nucleotide substitution that ends in early termination of the protein manufacturing process; usually due to a stop codon.

The most common alteration is a single base change or single nucleotide polymorphism (SNP)