Genetics II 2010

Genetics II 2010 - Genetics for Human Evolution Genome The...

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Genetics for Human Evolution Genome The total genetic endowment of a species The alleles you posses define your genotype or hereditary makeup. (The way they are expressed physically is your phenotype : the sum of observable traits)
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EVOLUTION This is the definition of evolution we will use: A change in the allele frequency of a population over time
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Where does the variation in populations come from? 1. Individuals vary as a result of sexual reproduction 2. Populations vary through time due to a number of factors we’ll cover today
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In all but the sex cells, genes come in pairs Any particular gene may display variants called alleles The ultimate source of alleles (variants) is mutation: a random change in the coding of a gene (that is, a change in the base pairs in codons) REVIEW Variation in individuals due to sexual reproduction
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in addition to Mutation, other sources of variation in individuals may also arise during sexual reproduction: Segregation (also called independent sorting) Linked genes Crossing over and the resultant Recombination
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Segregation / independent sorting: During the production of gametes, when allele pairs split into haploid gametes during meiosis, Each allele in a pair sorts independently from the other pairs: You don’t just get your grandmother’s alleles, for example: you get some of your grandfather’s
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YOU PARENTS GRANDPARENTS
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Linked genes However, instead of sorting independently, sometimes a segment of a chromosome will stay together
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Crossing over and Recombination And sometimes during meiosis, paired chromosomes may exchange material (crossing over). The result is a new mixture, a recombination.
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When one chromosome from the mother (with over 8 million possibilities) combines with one chromosome from the father (ditto), and this happens with all 23 chromosomes that is 2 to the 23 rd times 2 to the 23 rd , or about 70 trillion possible zygotes!
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But evolution is a process that involves change in POPULATIONS , not individuals, over time Population: a group of individuals that interbreeds
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We can genetically characterize populations by referring to the gene pool : the total genes of a population. One way to think about gene pool is to think of
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This note was uploaded on 10/04/2011 for the course ANTH 101 taught by Professor Simmons during the Spring '06 term at South Carolina.

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Genetics II 2010 - Genetics for Human Evolution Genome The...

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