Study Guide for Exam 1
Study Guide for Exam 1 012
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This 4 page Study Guide was uploaded by Amanda Notetaker on Sunday February 7, 2016. The Study Guide belongs to 012 at University of Vermont taught by Dr. Hill in Fall 2016. Since its upload, it has received 79 views. For similar materials see Exploring Biology in Biomedical Engineering at University of Vermont.
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Date Created: 02/07/16
CHAPTER 7.4 Meiosis: consists of two nuclear divisions; one DNA replication (Mitosis only has one round of nuclear division; cell is duplicated); Haploid cells produced are genetically diff from each other/parent 1. Meiosis I: homologous chromosomes line up together then separate - individual chromosome pairs separate while individual chromosomes (2 sister chromatids) stay together - 2 nuclei form each with half original chromosomes (Centromeres haven’t separated) 2. DNA Replication 3. Meiosis II: Sister chromatids separate à 4 non-identical haploid cells Genetic Variability Crossing Over (Recombination): (Prophase I) Homologous chromosomes and 4 chromatids form tetrad; homologs repel at centromeres but exchange genetic material at chiasmata à recombinant chromatids Independent Assortment: (Anaphase I) Depends on which homologous pair goes to which daughter cell Phases of meiosis that Mendel’s laws derive from: - Law of Segregation: The two copies of each chromosome separate causing the two alleles on the chromosomes to separate (Metaphase/Anaphase I) - Law of Independent Assortment: During metaphase I the random arrangement of chromosomes causes independent assortment of genes from separate chromosomes (Except linked genes that are close enough on same chromosome) How was Mendel lucky? - He used pea plants studying traits that had traits on separate loci, so he didn’t run into traits involving codominance/incomplete dominance - Pea plants are easy to grow/manipulate (has both male/female reproductive parts) - Law of Segregation assumes that each organism has only two copies of a gene, whereas polyploidy plants would have more than two copies CHAPTER 8/15 Recipe for Evolution: variation, selection, inheritability Monohybrid Cross: Plants differ in one character Hypothesis: irreversible blending à Law of Segregation: copies of gene separate during gamete formation P = RR x rr à F1 = 100% Rr (round) à F2 = 1 RR, 2 Rr (3 round), 1 rr (1 wrinkled) Dihyrbid Cross: Plants differ in two characters Hypothesis: Genes are independently distributed to offspring à Law of Independent Assortment: Alleles of diff genes assort independently P = RRYY x rryy à F1 = 100% RrYy à F2 = 9:3:3:1 (4 phenotypes) Test Crosses: used to determine if individual w/ dominant trait is hetero or homozygous by crossing unknown with a recessive partner If P homozygous à all dominant offspring If P heterozygous à 50% recessive Probability (1 = 100% certainty) Addition Rule: Probability of an event occurring in different ways, “or” Multiplicative Rule: Probability of 2 different outcomes happening together, “and” Expressivity: degree to which a genotype is expressed Ex: Person with mutant allele may get breast cancer and ovarian cancer while another only gets breast cancer à mutant allele has multiple expressivity Penetrance: proportion of individuals within a group that actually show expected phenotype Ex: Inheritance of mutant allele causes many, but not all, to develop breast cancer à mutation is incompletely penetrant Fitness: amount of offspring contributed to next generation by an individual Adaptive Evolution: presence/absence of trait increases fitness of individual/population (Trait evolves through natural selection) Types of Natural Selection: Stabilizing: favors average; purifying selection against deleterious mutations; Reduces variation Directional: favors those varying in one direction from average; confused w genetic drift Disruptive: favors those varying in both directions from average; increases variation à bimodal distribution of traits Hardy-Weinberg-Castle Equilibrium: null model in which allele frequencies don’t change over generations; genotype frequencies can be predicted Assumptions: No mutation/genotype selection/gene flow, Infinite population size, Random mating Violations: Evolution is occurring Allele Frequency: P = 2N AA + N Aa / 2N Q = 2N aaN Aa / 2N P + Q = 1 (N = # alleles) Genotype Frequency: AA = p , Aa = 2pq, aa = q 2 p + 2pq + q = 1 Four Horsemen of Evolution (Causes of Variation) 1. Mutation: random change in nucleotide sequences Synonymous (Silent): doesn’t change AA sequence Nonsynonymous (Missense): usually deleterious change to AA sequence Pseudogenes: non-functional copies of genes (function can return) 2. Selection: nonrandom mating 3. Gene Flow: change in allele frequencies due to migration of individuals/gamete movement between populations 4. Genetic Drift: random changes in allele frequencies between generations - Most powerful when population is greatly reduced in size (due to population bottleneck or founder effect) - Changes frequencies of neutral alleles in large populations Adaptation: favored trait evolves through natural selection; removal of deleterious mutations Incomplete Dominance: Heterozygotes have an intermediate/blended phenotype Ex: Red snapdragon flower + white à pink Codominance: heterozygotes show both phenotypes Ex: ABO Blood groups; Cows with patches Epistasis: Phenotypic expression of a gene is affected by another gene Ex: Fur color (Pigment presence à Color) CHAPTER 16 Synapomorphy: shared derived traits within a group; evidence of a common ancestor Homoplasies: traits identical in state, different in histories Ex: bat/bird from before Homology: features shared by multiple species that were inherited from common ancestor Evolutionary Reversal: trait reverts from derived state to ancestral state Convergent Evolution: superficially similar traits evolve independently in different lineages Ex: wing bones of bats/birds are homologous; wings are evidence of convergent evolution Monophyly: group includes ancestor and all descendants, no others (can be removed with a cut) Paraphyly: group includes common ancestor and some descendants Polyphyly: group does not include common ancestor Parts of a Phylogenetic Tree Lineage: series of ancestor/descendant populations; length of line represents time during which no divergent selection has occurred Node: single lineage splits into two; split represents speciation, duplication, transmission Root: common ancestor of all organisms in tree Taxon: group of species with a name Clade: any taxon that consists of all descendants of common ancestor (point of tree to terminal branches) Ingroup: primary interest - Outgroup: closely related to but phylogenetically outside of ingroup - Trait present in both groups = ancestral - Trait present in some of ingroup = derived Parsimony Principle: Preferred explanation for set of data is the simplest explanation - Minimizing # of evolutionary changes assumed over all traits in group - Best hypothesis is one with fewest homoplasies
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