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Susumu Ohno was one of the most famous developers of this theory in his classic book Evolution by gene duplication (1970). [26] Ohno argued that gene duplication is the most important evolutionary force since the emergence of the universal common ancestor. [27] Major genome duplication events can be quite common.
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]
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.
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.
Top: An ancestral gene duplication produces two paralogs (histone H1.1 and 1.2). A speciation event produces orthologs in the two daughter species (human and chimpanzee). Bottom: in a separate species , a gene has a similar function (histone-like nucleoid-structuring protein) but has a separate evolutionary origin and so is an analog.
In humans, chromosomes Y and 22 have the greatest proportion of SDs: 50.4% and 11.9% respectively. [2] SRGAP2 is an SD. 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 ]
Two examples of natural autopolyploids are the piggyback plant, Tolmiea menzisii [19] and the white sturgeon, Acipenser transmontanum. [20] Most instances of autopolyploidy result from the fusion of unreduced (2 n ) gametes, which results in either triploid ( n + 2 n = 3 n ) or tetraploid (2 n + 2 n = 4 n ) offspring. [ 21 ]
Gene duplication is a major mechanism through which new genetic material is generated during molecular evolution. For example, the olfactory receptor gene family is one of the best-documented examples of pseudogenes in the human genome. More than 60 percent of the genes in this family are non-functional pseudogenes in humans.