Amplification

Definition

Amplification is the selective increase of DNA copy number either intracellularly, as a local genomic change, or experimentally, by polymerase chain reaction (PCR). Increase of the level of mRNA or protein alone should not be referred to as amplification.

Characteristics

Intracellular amplification results in a selective increase in gene copy number with the consequence of elevated gene expression. Gene amplification has been seen in three different settings:

• Scheduled amplification as part of a developmental gene expression program, e.g., chorion genes in ovaries of the fruit fly Drosophila melanogaster or actin genes during myogenesis in the chicken.

• Unscheduled amplification during acquisition of cellular drug resistance. For example, amplification of the gene encoding dihydrofolate reductase (DHFR) can result in up to 1,000 gene copies per cell with the consequence of cellular resistance against the chemotherapy drug methotrexate.

• Unscheduled amplification of cellular...