Review questions for Exam 2 BIOL 3350 – Fall 2014 1. When a gene locus is not in Hardy-Weinberg equilibrium, we can conclude that some force of evolution is acting upon this locus to cause evolutionary change. What additional lines of evidence are used to provide us with clues about the likelihood of particular forces of evolution being responsible for the observed deviation from HWE? Offer several examples of the patterns in allele and genotype frequencies that one would expect under various forces of evolution. (tiger paper)If anyone understands this question and can relay it in more clear terms, it’ll be easier to answer. :-go over all the things on the slides that discuss factors that defy HWE(migrkation, gene flow, mutation, natural selection and how all of these things are related, all is well explained in 7.2 in book), my outline for this question is nearly a page long. 2. Natural selection and genetic drift can both result in the fixation of alleles. How are the two forces of evolution different even though the population genetic consequences may be the same? Under what conditions would you expect each to work most effectively and why? (tiger paper)· Genetic drift is random and natural selection is based on phenotype and forward moving and has more genetic variation to work on · Small population genetic drift and large for natural selection3. How do stabilizing and disruptive selection differ and how are each related to overdominance and underdominance respectively? Give examples of traits in natural populations that are favored by stabilizing and disruptive natural selection.Stabilizing selection results in over dominance and happens when the heterozygote of a certain allele is favored. n -shape graphDisruptive selection results in underdominance, where the dominant and recessive alleles are favored over the heterozygote. U- shape graph. 4. When natural selection is stabilizing, must heterozygotes always have the highest fitness? Why or Why not?No, just has to have the equal amount of (+) and (-) because only the phenotype is being acted on. Favors the intermediate phenotype 5. Explain how the balance between mutation and selection can actually lead to the maintenance of deleterious recessive or dominant mutant alleles. Demonstrate your answers mathematically and graphically.selection works on the phenotype and not the genotype so heterozygote is preserved because deleterious allele is covered and preserved (recessive mutant) q= square root (u/s)in dominant mutation, selection gets rid of mutant if selection rates are higher than drift q=u/s (q→ 0 quicker)6. You know that in a finite population, the probability that a neutral allele will achieve fixation from this point in time on is simply its relative frequency in the population. Summon your powers of deductive reasoning and tell us what is the probability that a brand new neutral mutant will be fixed in a population of N haploid individuals?diploid= 1/2N and haploid= 1/N7. In a multilocus system (with no dominance at each locus) all of the following genotypes are favored by stabilizing natural selection. Which are examples of overdominance (i.e., heterozygote advantage) and which are not? There are 10 loci and each + or – is the allele at the locus.1. + + + + + + + + + 3. + + + + – – – – – – – – – – – – – – – – – + + + +2. + + + + – – – – + + + + – – – –1. Completely heterozygous over dom2. Completely homozygous not an over dom genotype3. Heterozygote Overdominance, b/c the genes rotate Which of the three genotypes is most likely to increase in frequency under strong stabilizing selection when there is not heterozygote advantage? #28. Distinguish zygotic from gametic gene flow and offer an example of a taxon in which each islikely to be the dominant form of gene flow.Zygotic gene flow: Whole organism moves. diploid adults disperse to other populations and mates with the individuals with that population. Ex. Tigers dispersing from one population to another. Gametic gene flow: eggs or sperm move or haploid gametes disperse. Ex. Pollen in plants or group spawning events in marine invertebrates, frog eggs in the water.9. What are the specific genetic effects of inbreeding? Increased homozygosity by adding more autozygous individuals to a population. autozygosity is when you get the alleles from the same parent. Identity by descent. Exposes deleterious recessive alleles in homozygotes. What are the specific genetic effects of genetic drift? Increases the frequency of one homozygote, because it is making them all the same. How do the two processes differ in their genetic consequences? Which is more likely to cause deviations from Hardy-Weinberg equilibrium and why?Drift is causing evolution because it is the only one that causes the allele frequencies to change, changes P and Q. 10. What are the phenotypic effects of inbreeding and how do they arise? Is inbreeding alwaysbad for organisms in terms of mean fitness in a population? Why or why not?There is a decline in the average fitness of a population due to the exposure of deleterious recessive alleles exposed in an autozygous state. Inbreeding isn’t always badthough - it can be good if the organism lives in a constant environment. If the organism is a perfect fit for the constant environment, it is better to just make a bunch of copies of that organism so it will continue to thrive - plants “selfing”11. Consider the following two populations. Population A has about 10,000 breeding individuals while Population B has about 50 breeding individuals. In principle, should the outcome of directional natural selection be the same in each population? In practice, what is likely to happen? It is likely that Population B will become fixed faster than Population A due to the smaller number of breeding individuals.12. How strong must natural selection be, to overcome the effects of genetic drift in small populations? (tiger paper)When selection is greater than 1/Ne (1 over effective population)a. S > 1/Ne and selection rulesb. S < 1/Ne and drift rulesc. Example: If Ne= 100, then s > 0.01 before selection can increase favored allele13. It can be theoretically shown that one migrant per generation can provide enough genetic contribution to keep populations from differentiating locally. What are the genetic consequencesof gene flow among populations? Homogenizes