New User Special Price Expires in

Let's log you in.

Sign in with Facebook


Don't have a StudySoup account? Create one here!


Create a StudySoup account

Be part of our community, it's free to join!

Sign up with Facebook


Create your account
By creating an account you agree to StudySoup's terms and conditions and privacy policy

Already have a StudySoup account? Login here


by: Mr. Ana Muller


Mr. Ana Muller
GPA 3.54


Almost Ready


These notes were just uploaded, and will be ready to view shortly.

Purchase these notes here, or revisit this page.

Either way, we'll remind you when they're ready :)

Preview These Notes for FREE

Get a free preview of these Notes, just enter your email below.

Unlock Preview
Unlock Preview

Preview these materials now for free

Why put in your email? Get access to more of this material and other relevant free materials for your school

View Preview

About this Document

Class Notes
25 ?




Popular in Course

Popular in Biology

This 26 page Class Notes was uploaded by Mr. Ana Muller on Saturday September 12, 2015. The Class Notes belongs to BIOL 3000 at University of Georgia taught by Anderson in Fall. Since its upload, it has received 13 views. For similar materials see /class/202295/biol-3000-university-of-georgia in Biology at University of Georgia.


Reviews for EVOL BIOLOGY


Report this Material


What is Karma?


Karma is the currency of StudySoup.

You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 09/12/15
Genetic Drift GENEBJOL 3000 Genetic Drift We often think of gene frequencies changing in populations because natural selection or some other evolutionary force moves them Often in nature however gene frequencies change by chance in a process called genetic drif Genetic Drift Suppose only a few individuals contribute their genes to the next generation It is likely that the frequencies of alleles in offspring will differ just by chance from the frequencies in the parents Genetic Drift The smaller the sample of parents the more likely it is that gene frequencies in offspring will differ from those in the parents I This random change in gene frequencies due to the limited number of parents contributing offspring is called genetic drift History of Genetic Drift Process of random genetic drift seriously proposed as an important component of evolutionary change in the 1920 s and 1930 s by R A Fisher famous British statistician and geneticist Sewall Wright American geneticist adept at statistics and mathematics Importance of Genetic Drift Drift introduces the element of chance to evolutionary theory Not all evolutionary changes result from directional forces like natural selection Overall evolutionary process is a combination of chance and necessity Chance is largely drift Necessity is largely Selection Gene flow Genetic Drift of White and BI Frequency of Random Sampling of Gametes Genera on whim allele Adult parent Gen 0 0 03950 AleI39c frequencies in gamet same a 0 50 in adult parents Gen 0 Eamebes 39 1 060 060 Gen 2 Paren B 2 0 3980 Gen 2 Eamebes 03980 Randomly select 10 alleles to form 5 paremsquot I Gen 3 Paren B 3 0 4o Gene frequency changes are different for different population sizes ll 06 7V l IA fkgo mwaw l M quot f D Vex Vetivy W 39l ll 4 V N JUD Allulr 12139 lle 02 l Changes of allele frequencies under drift are larger for smaller population sizs l n o 2 N gt shows xation Variability of gene frequencies under genetic drift is higher for small population size Initial allele 2N frequency 1 392 N population size A Simulation Package Try your hand at simulating genetic drift and its joint effect with mutation and selection Just go to the link below and follow the instructions hH39n39lrlarwin PPh iirnnn 39 39 39 html Flvm seadie in Ecology amp Eioutionaly Biology at the UnVeIsty of Connecticut Population Biology Simulations onuma here m Yew stPlI slmulilmns u noulagymvmmus cams umnm sugga 7 lg n Population Genencs Mnlhervlls mwlunsmnusslun mm mmumn m Pavulnlmns EM algnmhm lama Vvguume may mm quoton a New 1 53mm con dlilnmm mum gums mm mummy uumumamnumum MqulncuxchnngnavsvhmlInImmholganhdnllmmmllPhpulhuns us me alanlmmm adwlnteulsramng allelalmquannasaw Ln DBLlivedWhvnx apulaunnslzasull 25 so mo 25mandlnraamnuenr mm ul wenavalmns 1mm mmmn mmw mu m swamHFKoalanxslmmulmnaremspmyzdmmmlunzauswmamammzmov unmmlialhchun ms wnmlallun mums hummus Mums Chung mum Inmiponsn honnmril nlwchan an mama gnanas ummyg mm m mnmmmwa um LIZHHIEIKRDH mreegenmgmnmmmmum Mm mu Rum 1mm up Io clamdwrvwmualmnxan dupllyidxvmulhnmmly m mm color n 4 applullluskmsme mummp um um Mammyan papmauan mm lms a asmlpll allJanus Mun mwdl n mmunn um mm M Nah I w my c m m my arm muses on m genehc mm m mmulzhon ulusnmnne lnmamun mm mm nlezlmnznd mm mm Usavsmiy mm hum m lumng allele rawm m m n as n n rm dllhvlnlpopulnon slzls no 25 so mo 250 Ind mm auralquotMummy 0 mo 2501 5 Wu u a wumunym n w Gineli mm mu 1 nm Inc a Hymn pap w n m 1 mvullulmlmal Ind llvz Wwb m mamm 5 u nmm luslvumm Genetic Drift p n jN leenevalmns WMM 1 7 JMJN Genevalmns Genetic Drift p ln v N w v Generations Wm v Start m mu m With 7 populations of 50 allels 4 went to xation and 3 remained polymorphic a er 100 generations Genetic Drift Over 250 Generations Only two ofeight populations still polymorphic n m V N Isn v Genevaiiuns 25 v can clear 1 l l l M Illll Wl M w l mum Relatively Little Genetic Drift in Populations of 1000 r los 4 N man u Genevalmns 250 v svanl Cleavl u WNW lv 39 Qt gt v J r W vmm WI AW v am With large N no populations xed after 250 generations Genetic Drift p luE Vin lln leenevaliuns lam vlSlarllCleav M gt r 5n Geneiahans With 10 alleles one of 7 populations was polymorphic after 50 generations Genetic Drift p lna le lun v Generations 25m v E Clear WM l WW fl WW W 25mm inventions Mth 1000 alleles 2 of 7 populations were polymorphic after 2500 generations Adel3 n Genetic Drift in Replicate Populations The tunes at the bottom represent the fraction of replicate populations having various allele frequencies These distributions braadenwith time Buri s Experiment on Genetic Drift Using Drosop Ya melanogaster 107 populations were started each with 8 females and 8 males all of them bw75bw heterozygotes two different Allululiwd I l l eye color alleles 39 In each 7 or ulation 8 females and 8 males were chosen randomly to found the next generation The populations varied in gene frequency already in Generation 1 l a The bw7S allele was rst lost in 39 quotwill a Population in Generation 6 r L llk39mdnn By Generation 19 allelef Mquot sky frequencies were more evenly distributed between 0 and 1 Bun39 did this research as a doctoral and the bw75 allele was lost or student with Sewall Wn39ght xed in more populations Genetic drift in 107 real populations of fruit flies D I Buri s populations consisted of 8 males and 8 females each generation Tharwafirnl hidvi kl IHAn Over the 19 generations in Buri s experiment heterozygotes decreased in frequency while both homozygotes Increased in frequency Mumhnval 3n Bumlitmus u Eenendan L u 2 3 s s 7 u 5 n papan c Heterozygosity In Buri s Populations m rm pmzeil s sgy 1 Expected frequency in g 05 populations of 1s ies 395 o n 1 3 04 H gt g i t39 a 3 n 0 a h 03 I gt 0 Theoretical prediction for t 393 populations of 9 ies x n o 3 g 02 I g o I 39U 3 01 Frequency of heterozygotes m 5 E 0 r r r r v 0 5 1 0 1 5 20 Generation Hum111 wounnnmu Expected Distribution from mathematical analysis of Allele Frequencies with Neutral S0 or Slight Selection Frequency of replicate populations a 05 g i u u i 05 m Allele frequency Allele frequency Notice that the small populations on the lelt are mostly drilling toward gene 39equencies of 0 or 1 Selection although weak skews allele 39equencies towards gene 39equency am in the examples on the right Under drift alone the Ushaped curve allele frequencies are clustered at 0 oral Migration or gene flow restores variability m amount of gene flow 2 populations N popula This graph what ha many populations of small size undergo s flow migration Fig 53 Dislribmian of 1111215 frequemm in a population will varying izmmml af i mmi gmli mi Coalescence is the newest way be study the effects of genetic drift Alleles diverge downwards with time and they can be viewed as coalescing upwards Gmea on 0 This diagram helps understand the conchE of Mitochondlial Eve and YChlomosome 2 o Generation 6 lo 0 l l Plesent Time Concept of Coalescence Number of oopies of gene A at time 0 They could be different alleles Most alleles go extinct over several generations By time t all oopies ofgene A desoended from a SINGLE ancestral allele at time 0 These alleles at time t said to CO ESCE to the anoestral allele Concept simple but powerful in evolutionary analysis ll l l i l21lil Aill 5 ll Mitochondrial Eve Current mtDNA type CAN be traced back to single female Normal aspect of sothgin phylogenetic trees Mitochondrial Eve A similar ch One mother oonstmcted for YChromosome Adamquot me Principles of Human Evolulion by Levvin and Finley Data on Y Chromosome Adam 167 mutations on Y chromosome More than 1000 men from 21 geographical regions Y chromosomes traced to Y of common ancestor Lived in Africa about 59000 a Data suggest humans left Africa more than once Fewer Y lineages survive today than mtDNA lineages Represents new field of archaeogenetics Mutation Drift Equilibrium Suppose we consider a population of limited size N For simplicity we assume Each of the N individuals contributes equal numbers of gametes to a pool of gametes Offspring are formed by drawing 2 gametes at random from this pool Genetic drift will of course occur Mutation Drift Equilibrium cont Suppose further that mutation occurs at the rate of u per locus each generation Let us suppose further that each mutation is to a new allele Let us use our concept of coalescence to find out how heterozygosity is related to N and u Look at the ancestry of alleles in 2 generations Gen t Allele in Parent Gen t 1 Alleles in Offspring With N individuals in Gen t there are 2N gene copies The probability that the two alleles in the next generation are copies of the same allele in the parent is just 1 2N Why Choose either parental allele Probability that the second is a copy of the same allele is 12N since the are N parents and 2N alleles Gen t Allele in Parent Gen t 1 Alleles in Offspring The only thing that could destroy this identity is mutation and either allele could have mutated Gent Allele in Parent Gen t 1 Alleles in Offspring Thus looking upward from Gen t1 to Gen t the two factors affecting identity are N the limited population size and mutation at rate u rupulatlull size causes coalescence with probability 12N and mutation destroys it with probability 2y because either allele could mutate So the probability of identity which is homozygosity is F12N 1 N 7 2N2y Let 6 Then heterozygosity 1 F 16 6 is an important quantity that tells us much about an evolving population Real Case of Genetic Drift Villages Towns and Cities in Italy Small villages and then larger and larger towns and cities in the Parma Valley of Italy were studied Frequencies of alleles for various blood types were determined from blood samples Migration was studied by comparing birth places of spouses This massive study was summarized in a book by CavalliSforza and his colleagues in 04 GENETIC VARlAnuN m Population Size and Genetic Drift Migration Measured as Distance Between Birth Places of Spouses Remember that migration among subpopulations of a metapopulation effectiver increases population size and thus reduces genetic drift High frequency of spouses from same parish opens possibility for drift in smaller populations 92 s 24 mam or Wimpmks a swe mm Variation for blood type alleles between villages is greatest for small populations clear evidence of genetic drift in u MOUNYAINS HILLS PLAle m39 GENFfIC VARIATION O 100 POPULATION DENSiTv European Land Snail Cepea nemoraI39s Shell color genetically determined and populations of the snail are polymorphic for color and for both number and width of bands Studies by French biologist LaMotte and others showed that both genetic drift and natural selection determine allele frequencies Futuyma page 225 Genetic variation at two enzyme loci in the house mouse Mus musculus in mice collected from scattered barns in Texas Each barn was considered a separate population TABLE 101 Frequency of alleles at two loci relative to population size of house mice Mean allele Variance of Es mated N lfnkei frequency allele frequencyquot population size sampled Es3b be B Bb be Small median 10 29 0418 0849 00506 01883 Large median 200 13 0372 0843 00125 00083 Rsearch by Selander The average allele frequency was not so different among the barns but the variation in allele frequency among barns was considerably larger in the small populations as expected under random genetic drift Futuvrna Table 10 1 21 Ernst Mayr one of the architects ofthe modern synthesis of evolutionary theory proposed that the FOUNDER EFF CT was an important but special kind of gene 39 39 n in a new environment it could lead to profound changes in a founder population VARIABILITY Fig 5 Loss and gradual recovery til genetic ation in a founder popula ion The formdcr B have only a iraciion of Lin g nc ic variation of the parental s ing genetic rcvaluiion TIME Vali c t pnpnlation A and fultlirtr genes are lost during the en u x in 39 uriati on l gruduallv recovered D if the population can nd a suitable niche until a new level E is reached Bottleneck and Founder Effect Population With equal frequencies of red and black alleles at Georgia locus Population size greatly reduced in bottleneck erhaps by environmental catastrophe or disease Frequency of red alleles now 80 The number of founders N0 and rate of increase r of the population together affect how much a population s level of heterozygosity is reduced after a bottleneck gtrozygusily pmcum r 10ND10 Inquot Time in gmarmlons mmww w Examples of Founder Effect Humans created a bottleneck in the 1890 s by hunting these seals almost to extinction As few as 20 individuals in late 180039s Population expanded to over 30000 But genetic variation greatly reduced can be seen y comparison with southern elephant seals which were not hunted so intensely Northern Elephant Seal 23 More on Northern Elephant Seals Mrounga angustrostrS Effective population size is smaller than the census size animal count because only a few of the large males compete successfully ror mates The winner of this contest will father all offspring of a harem of females 1 1 a Figure 105 Futuyma Founder Effect in terms of allelic diversity in the silvereye nquot m vduklonny AndyLil c my Pumn mum Mull In 24 The silvereye has colonized new islands in succession Norfolk Island 3 1 904 Auckland Tasmanla New Zealand South Island Flam1 murmmwmui ommmmmmimnc Allelic Diversity for 2oMainland 6 Microsatellite Loci noncoding short regions 15 Recent calonizations of DNA that are repeated g and loss of allelic diversity gt 3 10 3 E g 5 ML T SI CIPNA Nl Population Flaw74k smiuuunnmmw em Imanhnllnbhillu Founder Effect in Humans Amish founded community in Lancaster county Pennsylvania One oouple carried the gene for Ellis Van Creveld Syndrome Homozygous recessive allele Child with the syndrome has Shormned limbs 6 ngers on each hand Inbreeding in the isolated community has led to more affected homozygotes Both founder effect and inbreeding involved Another Founder Effect in Humans Dutch settled South Africa This Africaner population has high frequency of Huntington Disease Caused by dominant allele on chromosome Neuromuscular disorder Often strikes a er reproductive age By chance this allele represented at fairly high frequency in settlers


Buy Material

Are you sure you want to buy this material for

25 Karma

Buy Material

BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.


You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

Why people love StudySoup

Jim McGreen Ohio University

"Knowing I can count on the Elite Notetaker in my class allows me to focus on what the professor is saying instead of just scribbling notes the whole time and falling behind."

Allison Fischer University of Alabama

"I signed up to be an Elite Notetaker with 2 of my sorority sisters this semester. We just posted our notes weekly and were each making over $600 per month. I LOVE StudySoup!"

Bentley McCaw University of Florida

"I was shooting for a perfect 4.0 GPA this semester. Having StudySoup as a study aid was critical to helping me achieve my goal...and I nailed it!"

Parker Thompson 500 Startups

"It's a great way for students to improve their educational experience and it seemed like a product that everybody wants, so all the people participating are winning."

Become an Elite Notetaker and start selling your notes online!

Refund Policy


All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.