Population Genetics

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Population Genetics

Population Genetics Final Fall 2002 1Population GeneticsFall 2002Final ExamI. Briefly define/identify the following words and terms.1. effective population size2. soft selection3. altruism4. Hamilton’s rule5. epistasis6. allele7. inclusive fitness8. identity by descent9. autozygous10. carrying capacityII.Completely answer the following.1. The managers of a captive population of rare rodents want to preserve asmuch genetic variation over time as possible. They divide the populationinto 33 breeding groups, with 6 females and 2 males in each group. Fiftypercent of the females choose one male to sire their offspring while theother 50% choose the other male with which to mate. Males wereexchanged among groups each generation. After 30 generations of matingand dispersal the F ST (subgroups within the total) was 0.133, F IS(individuals within subgroups) was –0.085 and the F IT was 0.059. Thewildlife manager calls you and asks, “What do these numbers mean?” a)Write your answer. She is relieved to hear that the F IS is negative and shesays, “We have been trying to avoid inbreeding.” b) Should she berelieved? (Why or why not). She then wants to know if their managementtactics are working to maintain genetic variation. c) What do you tell her?You then ask her if she has tissue samples from the initial generation (33generations ago) in the freezer. d) Why did you ask that?2. A population of howler monkeys is comprised of many social groups.Within each social group are about 7 females and two breeding males inaddition to juveniles. After 12 generations you determine that the averagecoancestry within the social groups was 0.076 and the average correlationof genes between individuals from different groups was 0.022. Theaverage inbreeding coefficient was 0.01.i. What are the values of the F IS , F IT and F ST ? I=individual, S=Socialgroup, T=total population.ii. What proportion of the original (initial) genetic variation existswithin individuals?


Population Genetics Final Fall 2002 2iii. What proportion of the original genetic variation exists withinsocial groups?iv. What proportion of the original genetic variation exists within thetotal population?v. What proportion of the remaining genetic variation exists withingroups?vi. What proportion of the original genetic variation has been lost?3. A population has an inbreeding effective size (N e ) of 55.i. If N e remains stable over 50 generations, what will be the expectedinbreeding coefficient of the individuals?ii. The variance effective sizes over six years vary as follows: 40, 50,60, 30, 20, 15. What is the best estimate for the proportion ofgenetic variation that still remains within the population after thesix years?4. You return from a trip to Pakistan just six weeks before your researchreport in population biology is due. You are about to give up on it whenyou discover that you have brought back pelage lice with you. You count75 lice and suspect you were originally infected ten days ago. You couldeasily get rid of the lice with some insecticide, but you really need to do apopulation biology project. You read up on the species of louse and findthat they should increase at an intrinsic rate (r) of 0.075 per day. Theliterature says that these lice populations grow exponentially for the firstten days and thereafter are influenced by carrying capacity. A) How manylice did you likely receive when first infected? You calculate that yourcarrying capacity for the lice should be about 500. B) How many lice doyou expect to have on the day the research project is due?III. Calculate the following and provide interpretation.1. Your analysis of three populations resulted in the following genotypesPopulation I Population II Population III33 WW 12 WW 21 WW6 Ww 25 Ww 20 Ww11 ww 13 ww 9 wwA. Are the populations in Hardy-Weinburg equilibrium (critical X 2 =3.814)?B. What are the fixation indices (F IS , F IT , F ST )? What do these mean?C. What would be the maximum ratio of cost to benefit (c/b) in order for competitiveinteraction between individuals within the subgroup relative to the totalpopulation to be of genetic advantage?

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