Bio 152, Week 1 Notes
Bio 152, Week 1 Notes Bio 152
Virginia Commonwealth University
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This 4 page Class Notes was uploaded by Vania Notetaker on Monday September 5, 2016. The Class Notes belongs to Bio 152 at Virginia Commonwealth University taught by Alaina Campbell in Fall 2016. Since its upload, it has received 168 views. For similar materials see Introduction to Biological Science II in Biology at Virginia Commonwealth University.
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Date Created: 09/05/16
Week 1 Notes: Bio. 152 8/29-8/31 Core Concepts//People//Key Terms Section 21.1 The difference in DNA sequence is the reason we have genetic variation. Population Genetics – The study of the differences in DNA sequences/ genetic variation of a population Population – interbreeding species located in the same geographical area Species - interbreeding individuals with different combinations of alleles in a gene pool Gene Pool – Total alleles of all individuals in a species Sources of Genetic Variation ▯ Mutation; creates new variation ▯ Somatic (in body tissues) ▯ Germ-line (reproductive cells, passed thru generations) ▯ Can be deleterious (harmful), neutral or advantageous (beneficial) ▯ Recombination; shuffles mutations, making new combo. of mutations Section 21.2 Measuring Genetic Variation Population genetics makes statements about the evolutionary process using patterns of genetic variation When understanding patterns in genetic variation allele frequencies are key. Allele frequencies – rate of appearance of alleles in a population Ways to Measure Genetic Variation ▯ Observable traits ▯ Guessing genotype & phenotype ▯ Gel electrophoresis; separation of segments of DNA according to size ▯ Proteins (enzymes) ▯ DNA sequencing ▯ Displaying # of times mutation occurs in population of n diploid individuals Section 21.3 Evolution – a change in a population’s genetic make up over time. Genetic variation must be in a population for evolution to happen **Populations evolve not individuals** The Hardy-Weinberg equilibrium describes when evolution doesn’t occur. Conditions of H-W equilibrium ▯ No diff. in the survival & reproductive success of individuals (no selection) ▯ No adding or taking from the population by migration ▯ No mutations ▯ The population has to be large enough to prevent sampling errors (genetic drifts) ▯ Random mating H-W equilibrium equation – used to predict genotype frequencies using allele frequencies and vice versa 2 2 P + 2pq + q = 1 P = Homozygous Dominate(AA) 2pq = Heterozygous(Aa) q = Homozygous Recessive(aa) ** If you have p subtract it from 1 to get q and vice versa** If a population’s allele/genotype frequencies are not in equilibrium, evolutionary mechanisms are acting on the population and they’ve evolved If a population’s allele/genotype frequencies are in H-W equilibrium, evolutionary mechanisms are not acting on the population and they haven’t evolved Section 21.4 Natural selection leads to adaptation increasing the fit of organisms and their environment Population size, resources & competition determines who survives and leaves off-springs Darwin and Wallace figured out natural selection at the same time but credit it given to Darwin. Fitness - measure of representation of a genotype in next generation Mendel studied pea plants, with discrete traits meaning they had obvious alternatives As oppose to the traits studied by Mendel, most variations in populationscontinuous meaning they occur across a spectrum not having an obvious alternative. Ronald Fisher combined Darwin’s natural selection and Mendel’s genetics to create a Modern Synthesis; evolution Natural select increases frequency of advantageous mutation & reduce frequency of deleterious mutations Natural Selection can create a fixation of beneficial alleles meaning the allele frequency will be 1. All individuals in the population are homologous to said alleles. Positive Selection – natural selection promoting the frequency favorable alleles Negative Selection – natural selection removing of the frequency of harmful alleles Balancing Selection – maintains two or more alleles in a population ▯ Heterozygous advantage - heterozygous fitness is greater then either homozygotes, insuring both alleles in population Consequences of Natural Selection ▯ Stabilizing selection ; selection against extremes (keeps trait the same over time) ▯ Directional selection ; selection against one of two extremes (change in trait over time) ▯ Disruptive selection; selection against the mean ▯ Artificial selection; removal of competitive element and selection of successful genotype by a breeder, common in agriculture ▯ Sexual Selection; promotion of traits pertaining to an individuals reproductive opportunity Section 21.5 Migration, mutation and genetic drift are non-adaptive parts of evolution Migration – transport of allele from one population to another; lowers genetic variation ▯ Homogenizing can decrease fitness Mutation – the changing of gene structure ▯ Beneficial mutations spread ▯ Neutral mutations stay in for thousand of years ▯ Harmful mutations are removed within a couple generations Mutation in somatic cells; not passed on Mutation in germ cells; passed on Without mutation, genetic variation wouldn’t occur; so there’d be no evolution ** Mutation is rare** Genetic Drift – when allele frequencies’ goes up or done simple by chances ▯ Bottleneck- population with only a few individuals ▯ Founder event population started but only a few Gene Flow - transfer of alleles from one population to another Section 21.6 Molecular evolution is change in DNA/amino acid sequences The amount of time species have been isolated is how long it’s been since they shared an ancestor. Molecular clock – the correlation between amounts of time two species have been isolated and how much genetic divergences are between them **Molecular clocks can be used to date evolutionary events ** **Histone Molecular clock is the slowest** (Histone is the protein DNA wraps around to make chromatin) Pseudogene – No longer functional gene ▯ Molecular clock clicks the fastest
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