Evolutionary Bio Test 2 Week 3
Evolutionary Bio Test 2 Week 3 12050 - BIOL 3350 - 001
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This 4 page Class Notes was uploaded by Adam Rodenberg on Friday February 19, 2016. The Class Notes belongs to 12050 - BIOL 3350 - 001 at Clemson University taught by Dr. Michael Sears in Spring 2016. Since its upload, it has received 30 views. For similar materials see Evolutionary Biology in Biological Sciences at Clemson University.
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Date Created: 02/19/16
Evolutionary Bio Test 2 Week 3 This set of notes includes everything Dr. Sears covered in class plus all of the vocabulary and major notes from the textbook from this week. 2/16/16 Selection happens when individuals with particular phenotypes survive to sexual maturity at higher rates than those with other phenotypes, or when individuals with particular phenotypes produce more offspring during reproduction than those with other phenotypes Effects of lethal recessive alleles hard if not impossible to get rid of lethal recessive, they ‘hide’ in the heterozygotes Average fitness of populations selection on recessive alleles vs selection on dominant alleles Frequency dependent selection Know how selection acts on phenotypes, know “this frequency thing”, how many of a particular phenotype is in the environment effects the actual fitness Mutation typically too small to affect measurable evolutionary change Salt tolerance in flies experiment where food meat had lots of salt in it would kill them, eventually the ones that lived from the salt resistant ones produced offspring that were selected for a higher % of the population that had the salt resistance Know example of Medea, Know example of CF and typhoid in humans, will go over in review session Migration some members of a species moving from(example) a large continent to small island, migration can have a homogenizing effect Nerodia snake example in Lake Eerie islands have greatly varying frequencies of body patterns (striped, checkered, plain, mixed) Effects of genetic drift 1. Because the fluctuations in allele frequency from one generation to the next are caused by random sampling error, every population follows a unique evolutionary path. 2. Genetic drift has a more rapid and dramatic effect on allele frequencies in small populations than in large populations. 3. Given sufficient time, genetic drift can produce substantial changes in allele frequencies even in populations that are fairly large. Gone over selection, selection/mutation balance, drift, Know the math!, be able to put things in and manipulate and come up with an answer, quiz Thursday 2/18/16 Heterozygosity= 2pq Know Chi square test, know all the math, do all the worked out problems on minmeister, Probability of fixation p(fixation o fA1) = x/(2N) Heterozygosity is the frequency of heterozygotes in a population In smaller populations, organisms will drift away from high heterozygosity and move towards consistently selecting one allele over the other Effective population size drives drift not the actual size Ne= (4NmNf)/(Nm+Nf) Decrease in heterozygosity can be bad for populations Genetic polymorphisms the fraction of loci within the genome that have at least two alleles with frequencies higher than 0.01, increased with population size in nature Allelic richness number of alleles on a given locus Small pop. sizes in nature do cause fixation in nature Rate of evolution when only genetic drift is working; when new alleles created by mutation are substituted for other alleles already present This rate of evolution is = the mutation rate 2Nv * (1/2N)=v v= the rate of neutral mutations Selection vs natural processes (1) Deleterious alleles appear and are eliminated by selection; (2) Neutral mutations appear and are fixed or lost by chance; and (3) Advantageous alleles appear and are swept to fixation by selection. Smaller populations follow more diverse evolutionary paths when they are under selection and genetic drift Neutral theory as a null model neutralist selectionist controversy is a debate where the relative importance of drift and positive selection in explaining molecular evolution Inbreeding depression negative effects from inbreeding Textbook Vocab Ch. 7 Sampling error when the statistical characteristics of a population are estimated from a subset, or sample, of that population Random genetic drift sampling error in the production of zygotes from a gene pool Founder effect the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population Heterozygosity frequency of heterozygotes in a population Fixation index (F ST a measure of population differentiation due to genetic structure Effective population size the size of an ideal theoretical population that would lose heterozygosity at the same rate as an actual population of interest Substitution the fixation of a new allele, with or without additional mutational change Genetic drift the change in the frequency of a gene variant in a population due to random sampling of organisms Neutral theory formulated by Kimura, saying that effectively neutral mutations that rise to fixation by drift vastly outnumber beneficial mutations that rise to fixation by natural selection Silent site (synonymous) mutations DNA sequence changes that do not result in an amino acid change Replacement (nonsynonymous) mutations sequence changes that do result in an amino acid change Negative / purifying selection natural selection that eliminates deleterious alterations before they become common Positive selection selection for beneficial mutations that increases their frequencies Polymorphism a locus at which individuals in a population carry different alleles Codon bias differences in the frequency of occurrence of synonymous codons in coding DNA Hitchhiking / selective sweep the reduction or elimination of variation among the nucleotides in neighboring DNA of a mutation as the result of recent and strong positive natural selection Background selection results from negative selection against deleterious mutations Coalescence merging of genealogical lineages as we trace allele copies backward in time Gene tree / gene genealogy the use of DNA testing in combination with traditional genealogy and traditional genealogical and historical records to infer relationships between individuals Inbreeding mating among genetic relatives Coefficient of inbreeding (F) the probability that the two alleles in an individual are identical by descent Inbreeding depression the reduced biological fitness in a given population as a result of inbreeding CH. 8 Haplotype multilocus genotype of a chromosome or gamete Linkage equilibrium two loci in a population Linkage disequilibrium when there is a nonrandom association btwn a chromosomes genotype at one locus and its genotype at the other locus Genetic recombination the creations of new combinations of alleles during sexual reproduction Extended haplotype homozygosity (EHH) the probability that two randomly chosen chromosomes carrying the core haplotype of interest are identical by descent (as assayed by homozygosity at all SNPs) for the entire interval from the core region to a distance Parthenogenesis a mode of reproduction in which offspring develop from undeveloped eggs Genetic load the burden imposed by the accumulating mutations when an asexual population’s average fitness is decreasing over time
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