Lynch et al 2001 genetics 159 1789 every genome

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Unformatted text preview: in gene number Much of the variation in eukaryotic genome size is due to repetitive DNA In Bacteria, genome size predicts gene number, but not so in Eukaryotes one gene in bacteria equals one KB of genetic information. Where do new genes come from? duplication events are the most common resource for the genome to create new functional genes. Most new genes arise from duplications “Newly emerging data from genome sequencing projects suggest that gene duplication, often accompanied by genetic map changes, is a common and ongoing feature of all genomes. This raises the possibility that differential expansion and contraction of various genomic sequences may be just as important a mechanism of phenotypic evolution as changes at the nucleotide level.” Lynch et al. (2001) Genetics 159: 1789 Every genome contains duplicated genes (paralogs) again gene duplication is though to be the biggest source of adaptive evolution. How do duplications occur? Whole genome duplication (autopolyploidization) - nondisjunction of all chromosomes; gametes have twice the ploidy Segmental (gene) duplications - mostly small, involving 1 or few genes Naturally, this will be most common in those animals & plants capable of self- fertilization when chromosomes separate in meiosis both sets of DNA go to one pole of the cell, normally triploidy causes death. In the 1970s, Susumu Ohno proposed that gene duplication was the basis for innovation in evolution, by providing new genetic material predisposed towards new functions. He hypothesized that that there were two rounds of whole genome duplication (the 2R hypothesis) in the evolution of vertebrates; the first occurring before, and then one after, the divergence of tetrapods and fish, about 430 mya. And it turns out that Oh...
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