BISC 121Lg Chapter Notes - Chapter 23: Secondary Sex Characteristic, Intron, Microevolution

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30 Sep 2016
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Microevolution- a change in allele frequencies over generations. Chapter 23 notes: caused by natural selection, genetic drift (chance events that alter allele frequency), and gene flow (transfer of alleles between populations) Genetic variation- differences among individuals in their genes: can be measured by percent of heterozygous loci, can be measured at gene level. Very little of this results in phenotypic differences because of introns (noncoding regions of dna: relies on mutation, gene duplication, etc. Majority of animal mutations happen in somatic cells and are not passed on. Point mutation- change in one base of a gene. Most phenotype altering mutations are slightly harmful: usually taken out by natural selection but could survive through heterozygous protection. Neutral variation- dna changes that give no disadvantage or advantage. About 1 mutation occurs per 100,000 genes per generation. Sexual reproduction creates a lot of unique genotypes: crossing over, independent assortment, and fertilization. Population- group of same species individuals that live together and interbreed.

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