BIO3400 1nd Edition Exam 1 Study Guide Lectures 6 8 Lecture 6 I Thomas Morgan Mutation a Early 1900s b Mutations occur every generation c Mutations can occur anywhere in the genome d On a per individual per gene basis mutations are incredibly rare i 2 10 8 II Gregor Mendel Inheritance a 1865 pea experiments published b Early 1900s work rediscovered c Laws of Mendelian Inheritance III The Modern Synthesis a Included 2 major reconciliations 1936 1947 i Medndelian genetics with natural selection and gradual evolution ii Microevolution with macroevolution IV The Simplest Model a single gene a Peppered moth b Color morph is determined by a single gene c Dark allele 0 1 d Light allele 0 9 i Frequency does not tell the PREVELANCE I Allele frequencies do not tell you anything about dominance II Not all allelic interactions are characterized by dominance III Hardy Weinberg Equilibrium a The expectations for genotype frequency if no outside forces are acting on the population p2 2pq q2 b The expectations for allele and genotype frequencies over time if no outside forces are acting on the population no change c Assumptions infinite population size random mating no migrant no mutation no selection IV Peppered moth evolution a During the industrial revolution mid 19th century pollution led to the following changes in England i Death of light colored lichen ii Soot covered many of the tree trunks iii As a result moths began to select for dark colored allele slowly V Why do we need a more complex model a What can be explained with a single gene model VI VII i One allele replacing another after this need mutation ii Limited range of variation b Limitations i Natural selection can only fine rune in a limited range ii Further evolutionary change independent on mutation iii Not consistent with natural selection leading to macroevolution What taxonomic level shows this level of variation a Kingdom phylum class order family genus species b Dog domestication began 10 000 years ago most breeds originated within hundreds of years ago c Diversification of the Canidae family began 55 million years ago d Mutation rates are too low to account for the amount of change produced by artificial selection e Selection can result in phenotypes outside the original range of variation f Significant change can occur rapidly g A single locus model of selection can t account for these observations Quantitative Traits and Polygenic Inheritance a Most traits are polygenic i Do not conform to discrete categories ii Do not display usual 3 1 1 1 or 1 2 1 ratios Lecture 7 I Quantitative Genetics and Heritability a One challenge is quantifying how much phenotypic variation is due to variation in genetic factors and how much is due to variation in environment b Heritability the fraction of the total variation in a trait that is due to variation in genes c What would happen if we planted many clones genetically identical individuals in different fertilizers and selected on plant size II Genes versus Environment a Genes only operate within an environment these cannot be disentangled within an individual b Heritability is a population parameter c What percentage of the variation in the population is due to variation in genetic factors YES d What percentage of the height for an individual is because of their genes NO III Variation a Heritability the fraction of the total variation in a trait that is due to variation in genes b Variation Summation fruit size mean fruit size 2 number of fruits 1 c Heritability Vg Vg Ve Vg Vp i Vg genetic variance ii Vp total variance phenotypic variance iii Ve environmental variance IV 2 types of heritability a Broad sense H 2 b Includes all genetic effects c H 2 Vg Vp d Narrow sense h 2 more important parents only pass an allele not a genotype e Includes only additive genetic effects f h 2 Va Vp g Alleles are passed on not genotypes therefore only additive effects are passed on V Measuring Heritability a Based on the observed and expected resemblance among relatives b Slope of the best fit line h 2 c Actual genetic similarity in a lab d Familiar similarity twins identical and fraternal VI The Breeder s Equation Predicting the response to selection a R Z h 2 S b Response to selection heritability selection differential VII The Selection Differential a What is S b S Mean breeders mean population c S 0 0 9 0 9 VIII R is the change in the mean trait value a New old IX Summary a The genetic component of quantitative traits can be estimated by looking at the phenotypic similarity of relatives b This estimate enables you to predict how a population will respond to selection c The magnitude of the response is directly proportional to the heritability for the trait in question d Quantitative genetics allows you to understand the genetic basis of virtually all aspects of the phenotype even if you do not know the specific genes involved Lecture 8 Sources of Genetic Mutation Mutation is the only source of new genetic variation o Mutations are random o The vast majority of mutations are deleterious reduce fitness or are neutral o Few mutations are beneficial o Mutation rates vary among species and populations o Mutation rates evolve just like other traits generally pretty low Sex and Genetic Recombination Sex creates new genetic combinations every generation 23 pairs of chromosomes 2 23 over 8 million combinations for each pair of parents crossing over creates even more combinations no two humans will ever have the same genetic makeup except clones offspring can have phenotypes outside the parental range populations have a lot of standing genetic variation mutation is an ongoing process that contributes to standing variation the process of evolution typically does not rely on new mutations