gene amplification

n.
A cellular process characterized by the production of multiple copies of a particular gene or genes to amplify the phenotype that the gene confers on the cell. Drug resistance in cancer cells is linked to amplification of the gene that prevents absorption of the chemotherapeutic agent by the cell.

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The process by which a cell specifically increases the copy number of a particular gene to a greater extent than it increases the copy number of genes composing the remainder of the genome (all the genes which make up the genetic machinery of an organism). It is therefore distinguished from duplication, which is a precise doubling of the genome preparatory to cell division, and endoreduplication, which leads to endopolyploidy.

Gene amplification results from the repeated replication of the deoxyribonucleic acid (DNA) in a limited portion of the genome, in the absence of or to a much greater extent than replication of DNA composing the remainder of the genome. Thus is formed a cell in which the genes composing a limited portion of the genome are present in relatively high copy number, while the genes composing the remainder of the genome are present in approximately normal copy number. See also Deoxyribonucleic acid (DNA).

Since gene amplification increases the copy number of a specific region of the genome without altering the copy number of genes composing the remainder of the genome, it would appear to offer an alternative method for developmental control of gene expression. By increasing the number of copies of a particular gene, the number of gene copies available for transcription could thereby be increased.

In a number of instances of gene amplification, the amplification phenomenon appears to be developmentally regulated, and the amplified copies of the gene are subsequently lost from the cell. Studies on cells in culture have demonstrated “amplification” of genes involved in resistance to specific drugs. See also Gene; Gene action.

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n.

A cellular process characterized by the production of copies of a gene or genes to amplify the phenotype that the gene confers on the cell.

A process in a cell by which a particular gene is replicated so that more copies are available to produce a protein for the cell's use. For example, the genes that code for proteins involved in ribosomes are amplified early in the process of cell development so that there are sufficient numbers of them to assemble the cell.

PCR, polymerase chain reaction, can be considered a type of man-made gene amplification process.

the selective, repeated replication of a certain gene or genes without a proportional increase in other genes in the genome. It occurs, e.g., in the DNA puffs of Rhynchosciara and some other flies and in the genes encoding ribosomal RNA (so-called ribosomal DNA) in amphibian oocytes. The mammalian dihydrofolate reductase gene is amplified in cells selected for resistance to increasing concentrations of methotrexate.

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