Chapter 24

Chapter 24 - Chapter 24 Evolution of Genes and Genomes 24.1...

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Chapter 24: Evolution of Genes and Genomes 24.1 – How are genomes used to study evolution? o A genome is the full set of genes an organism contains o Mutations supply the raw material for evolutionary change o The capacity to cooperate with other genes increases if a gene is stable in a population o Genes of an organism are like interacting members of a group o Molecular evolution investigates mechanisms and consequences of the evolution of macromolecules o Evolution of nucleic acids and proteins depend on genetic variations o One form of variation is called nucleotide substitutions o Nucleotide substitutions sometimes lead to an amino acid substitution that may lead to a phenotypic difference o The longer two sequences have been evolving have been evolving separately, the more different they will be o Homologous features are shared by homologous proteins which are represented by their nucleotide sequences o Therefore to determine similarities, we can look at the sequences o Sequence alignment techniques help us compare protein sequences to determine homologous traits o Gaps can occur too in addition to substitutions o A similarity matrix tells us the minimum amounts of changes that had to have occurred between the organisms o There are several reasons why the similarity matrix isn’t the correct number of changes that occurred Multiple substitution – more than one change occurs at the same locus Coincident substitution – diff substitutions occur at same locus in two organisms Parallel substitution – same substitution occurs at same locus in two organisms Back substitution – substitution occurs and goes back to original sequence
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o To track these changes effectively, biologists have created models that describe how DNA typically evolves o These models take into account the rate of transitions (changes between two purines or two pyramidines)and transversion (changes between a purine and a pyramidine) o Using these models, we cane estimate the total number of substitutions that occurred
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This note was uploaded on 09/08/2011 for the course LS 1 taught by Professor Thomas during the Summer '05 term at UCLA.

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Chapter 24 - Chapter 24 Evolution of Genes and Genomes 24.1...

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