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Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene .
Evolution by gene duplication is an event by which a gene or part of a gene can have two identical copies that can not be distinguished from each other. This phenomenon is understood to be an important source of novelty in evolution, providing for an expanded repertoire of molecular activities.
The 2R hypothesis saw a resurgence of interest in the 1990s for two reasons. First, gene mapping data in humans and mice revealed extensive paralogy regions - sets of genes on one chromosome related to sets of genes on another chromosome in the same species, indicative of duplication events in evolution. [9]
Misalignment of LCRs during non-allelic homologous recombination (NAHR) [3] is an important mechanism underlying the chromosomal microdeletion disorders as well as their reciprocal duplication partners. [4] Many LCRs are concentrated in "hotspots", such as the 17p11-12 region, 27% of which is composed of LCR sequence.
Single gene duplication is a random process and tends to make duplicated genes scattered throughout the genome. Duplicated blocks are non-overlapping because they were created simultaneously. Segmental duplication within the genome can fulfill the first rule; but multiple independent segmental duplications could overlap each other. [18]
[6] [7] [8] Gene redundancy has long been appreciated as a source of novel gene origination; [8] that is, new genes may arise when selective pressure exists on the duplicate, while the original gene is maintained to perform the original function, as proposed by newer models [4]. Figure 1. Common mechanisms of gene duplication.
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A gene family is a set of several similar genes, formed by duplication of a single original gene, and generally with similar biochemical functions. One such family are the genes for human hemoglobin subunits; the ten genes are in two clusters on different chromosomes, called the α-globin and β-globin loci.