LIFESCI 4 Chapter Notes - Chapter 25.4 - 25.5: Eukaryote, Archaea, Horizontal Gene Transfer
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25. 4 much of an organism"s evolutionary history is documented in its genome (1) Molecular systematics enables scientists to compare genetic divergence within a species. Gene duplication provides opportunities for further evolutionary changes: these homologous genes are distinguished by different names. Orthologous genes: homologous genes passed in a straight line from one generation to the next but have ended up in different gene pools because of speciation. Paralogous genes: homologous genes found in the same genome due to gene duplication. Orthologous genes are widespread and can extend over huge evolutionary distances. All living organisms share many biochemical and developmental pathways. Genes in complex organisms are extremely versatile and each gene can perform many functions. Paralogous genes, number of substitutions is proportional to the time since the genes became duplicated. Rate of clock may vary greatly from one gene to another; some genes evolve a million times faster than others.
