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Unformatted text preview: 25.4 Much of an organism’s evolutionary history is documented in its genome Gene Duplications and Gene Families Genome Evolution • Molecular systematics – comparing nucleic acids or other molecules to infer relatedness – is a valuable tool for tracing organism’s evolutionary history • The molecular approach helps us to understand phylogenetic relationships that cannot be measured by nonmolecular methods such as comparative anatomy • It enables scientists to compare genetic divergence within a species • The ability of molecular trees to encompass both short and long periods of time is based on the fact that different genes evolve at different rates, even in the same evolutionary lineage • Gene duplication is one of the most important types of mutation in evolution b/c it increases the number of genes in the genome, providing opportunities for further evolutionary changes • The molecular phylogenies of gene duplication and the influence of these duplications on genome evolution can now be followed in detail o These phylogenies must account for repeated duplications that have resulted in gene families • The term orthologous genes (from the Greek orthos , straight) refers to homologous genes that are passed in a straight line from one generation to the next but have ended up in different gene pools because of speciation • Paralogous genes (from the Greek para , at the side of) result from gene duplication, so they are found in more than one copy in the same genome • Orthologous genes can only diverge after speciation has taken place, w/ the result...
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- Fall '08
- Evolution, Molecular Clocks