Evolution Notes: Week Three
Evolution Notes: Week Three BIO318
Virginia Commonwealth University
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This 5 page Class Notes was uploaded by Jayda Abrams on Saturday September 17, 2016. The Class Notes belongs to BIO318 at Virginia Commonwealth University taught by Dr. Turbeville in Fall 2016. Since its upload, it has received 9 views. For similar materials see Biology: Evolution and Biodiversity in Biology at Virginia Commonwealth University.
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Date Created: 09/17/16
Week Three Tuesday 9/13/16 Thursday 9/15/16 Hardy Weinberg Evolution- The evolution of a population, not an individual. The change in allele frequencies from generation to generation. Equlibria- two sides are equal in flow of change. When no change in an equation or in a model we say it’s at a state of equilibrium. When something reaches equilibrium it will stay there for infinite amounts of time until something changes. Types of Equilibrium: Stable Equilibrium- 2 conditions at equilibrium: 1) It doesn’t change 2) if it is displaced the system will return to its original state. Unstable Equilibrium- 2 conditions when at equilibrium: 1) It doesn’t change 2) if it is displaced then the system will not return to the original position. Neutral Equilibrium- 2 conditions when at equilibrium: 1) It is stable 2) if displaced then it will move to a difference equilibrium. Mixed Equilibria- Combo of 3 types. When at this point it doesn’t change, depending on which way it is disturbed depends on where the equilibria lands. Hardy- Weinberg is mixed! Null models- Useful in evolution and ecology. A null model is = population model where change does not occur. Nothing is happening (Ex: Migration, drift, selection, mutation). It is the simplest model and the simplest explanation for a data pattern. Hardy- Weinberg Model- Tells what happens to the genotype and allele frequencies when nothing besides reproduction is occurring. Question: Which of the following is assumed? Answer: Mating is random Mutation is absent Natural selection is not occurring Gene flow is not occurring Population is large (mathematically infinite) Hardy-Weinberg Equilibrium = HWE Equilibrium occurs within one generation of random mating and return back to equilibrium. Frequency = f[ ] If everything is known it will sub to 1. If it doesn’t a mistake was made! And = multiply or = add Genotype frequency is stable and allele frequency is neutral. Genotype frequency is a function of allele frequency, that is why genotype frequency is stable and allele frequency is neutral. Example 1: Know Find 100 plants are red and white HWE genotype frequencies 25 are white F(a1a1) Singe locus 2 alleles F(a2a2) At HWE F(a1a2) The only genotype with white flowers can be a2a2. Example 2: Know 100 plants F(a1a1) = .50 F(a1a2)=.25 F(a2a2)=.25 Is this population at HWE? Mutation Rate Rate = change in quantity over time. Example the number of mutations and time that has passed (Official definition on page 270). Types of mutations 1. Point mutation: single nucleotide (ex: ACTTCT). Where a point mutation occurs determines the likelihood of changing a protein sequence. Usually in the 3rdposition it will not change the amino acid. However the 1 position usually does change the amino acid. Types of point mutations: Start and Stop codons Exons- Code for proteins by making messenger RNA Introns- Don’t code for anything but still part of a gene Frameshift Nonsense/ missense- AKA synonymous/ Nonsynonymous (ex: a change to a codon that changes the amino acid is nonsynonymous). Transition- Change that keeps different bases as purine to purine or pyrimidine to pyrimidine. Transmission- Purine Pyrimidine. 2. Insertion- Deletion: block of nucleotides deleted or inserted also known as InDels (Ex: ACT no ACT = Deleted ACT ACCT C was inserted). 3. Frameshift- InDel in genes that changes the order. This can have a major effect and this type of mutation and creates a lot of diseases. Selfing- An extreme form of inbreeding. Defined as mating with yourself. Humans cannot self but some plants and animals can. When heterozygotes self they do not always make heterozygotes. With selfing the frequency of heterozygotes decreases. Frequency of homozygotes do not change but the genotype frequencies do change. In diagrams the top has never inbreeded and the bottom is only from inbreeding. F would be equal to the proportion of total gamete pool that is inbred andF-1 would be equal to non-inbred.
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