DOC PREVIEW
UNC-Chapel Hill BIOL 201 - Hardy-Weinberg Equilibrium

This preview shows page 1 out of 4 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 4 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 4 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

BIOL 201 1st Edition Lecture 2Outline of Last LectureI. Myths of Evolutiona. Definition of Scientific Theoryb. Definition and myths of evolutionc. Natural selectionII. Phenotype vs. GenotypeIII. Discrete TraitsIV. Genotype and Allele FrequencyOutline of Current LectureI. Hardy-Weinberg Equilibriuma. AssumptionsII. MHC Loci Examplea. Possible ExplanationsIII. HeterozygosityIV. Continuous Traitsa. Meanb. Variancec. Coefficient of Variationd. CorrelationV. Variation a. Phenotypicb. GenotypicVI. Heritability a. Broad sense vs. Narrow senseVII. Brief history of evolutionary thoughta. Greeksb. Christian Theologyc. Pre-Darwinian evolutiond. Charles DarwinCurrent LectureI. Hardy-Weinberg Equilibrium: If a population is free from evolution (microevolutionary forces like mutation, migration, and natural selection)then allele frequencies won’t change. The proportions f(AA) = p2 f(Aa) = 2pq and f(aa) = q2 where p = f(A) and q = f(a) will occur for genotype frequencies.i. In normal population, HW proportions are always present afterrandom mating until something else happens  evolutionii. Equilibrium is reached if you magically stop evolutioniii. Can use departure from HW equilibrium to prove that evolutionary forces are actingb. Assumptionsi. Infinite population size (no genetic drift), no selection, no mutation, no migration, and random mating which means no sexual selection. II. MHC Loci Example: Do genotype frequencies at the MHC loci of humans conform to the HW model?i. MHC is part of immune system and locus is used in pathogen regulationii. Shows way more heterozygotes at both loci studied than expected which shows that some kind of evolutionary force is actingiii. Can’t tell from this what specific force that isb. Possible Explanationsi. Non-random mating  humans may be able to sense MHC and therefore chose mates based on which they haveii. Natural selectioniii. Can’t tell which explanation it is though. The first step is to determine if HW proportions are present in detecting evolution.III. Heterozygosity: average of how many heterozygotes there are arounda. Heterozygotes have one type while there are two homozygote types (AA and aa).b. Low heterozygosity indicates a very small population that is usually under genetic driftIV. Continuous Traits – like height, weight, or length of a tail, shows normal distribution bell curve, and more people leads to a more normal distributiona. Meanb. Variance: determines how fast a population can respond to evolutionary change and is a departure from the meanc. Coefficient of Variation: makes variance unitless so that you can compare objects/things of different sizesd. Correlation: measures how 2 related variables are to one anotherV. Variation  evolution requires genetic variation but not all variation is important for evolution.a. Phenotypic = genetic variation + environmental variationi. VP = VG + VE b. Genotypic = (also called genetic) additive genetic variation + dominance or non-additive genetic variation; is important for evolutioni. VG = VA + VDii. Additive variation is important part of equation because it describes the variance that is actually passed from parent to offspringiii. Natural selection can only act on variation that is phenotypically apparent and if there’s no evolution then additive variation doesn’t change.iv. Genetic variation can be lost due to selection when one particular side of distribution is favored/unflavored; it’s generated by mutation and recombination.VI. Heritability a. Broad sense vs. Narrow sensei. Broad sense = VG/VPii. Narrow sense  h2 = VA/Vp*h is not squared, just written that wayiii. Evolution is really only affected by narrow sense heritability, it determine the relationship btwn the parent and the offspring generationiv. If there’s no relationship then there’s no heritability. If can perfectly predict then heritability is 1.v. Narrow-sense heritability is the slope of a graph of midparent phenotype vs. midoffspring phenotypevi. Midparent and midoffspring just means average of the phenotype between both parents or all offspringVII. Brief history of evolutionary thoughta. Greeks pre-evolutionary thoughti. Plato: didn’t think things changed at all or were related at allii. Aristotle: linear scale of life like a factory; everything is put together to look the same but there are slight differences due toerrorsb. Christian Theologyi. John Ray: idea that living things could be classified logically, evolutionary theorist, believed it was all God’s thought, early naturalist and systematistii. Carl Linnaeus: came up with system of classification with genus, species, etc., creationists, species made by God and others come from cross-breeding iii. Louis Agassiz: believed that world was NOT static so there were ice ages and things like that , big Darwin critic and staunch creationistc. Pre-Darwinian evolutioni. George-Louis Leclerc de Buffon: alterations of animals over time but not over the lifespan of one animalii. Believed that species classification is human invention and merely a way to organize thingsiii. Thought changes were degradationsiv. Homology: same components with different functions show relationship between organismsv. Jean-Baptist Lamark: PhilosophieZoologique; all organisms change with time, inheritance of acquired characteristics1. Ex: thought ancestor of a giraffe reached up to get food from top of tree so produced offspring with a long neckd. Charles Darwin: naturalist, name/face of evolutionary theoryi. Went of Voyage of Beagle to gather most of evidenceii. Strongly influenced by Lyell’s geologic idea that the physical world changed (plate tectonics)iii. Influenced by Malthus as well who thought world was overpopulated and would run out of resources without famine, war, and diseaseiv. These influences plus communication with Wallace lead to ideas of natural selection v. Wallace had same idea as Darwin did before Darwin published but had done less research to back it upvi. On the Origin of Species by Natural Selection was Darwin’s big evolutionary publication1. Thesis 1: all species descended from 1 or a few original life forms, macroevolutionary2. Thesis 2: natural selection is primary driver of evolution; didn’t understand genetics yet so had some holes in


View Full Document

UNC-Chapel Hill BIOL 201 - Hardy-Weinberg Equilibrium

Download Hardy-Weinberg Equilibrium
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Hardy-Weinberg Equilibrium and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Hardy-Weinberg Equilibrium 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?