DOC PREVIEW
UM BIOB 272 - Populations Genetics (drift) Day 2
Type Lecture Note
Pages 6

This preview shows page 1-2 out of 6 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 6 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 6 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 6 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

BIOB 272 1st EditionLecture 17 Outline of Last Lecture Population Genetics (drift)I. Relaxing the assumptions of Hardy-Weinberg Equilibrium ModelII. Mutationa. Important Termsi. Mutationsii. Polymorphismsiii. Genetic drifiv. Substitutionb. Molecular Basis of Mutationsc. Point MutationsIII. Single Nucleotide Mutations in Genesa. Nonsense Mutationb. Missense Mutationi. Transitionalii. Transversionalc. Frameshif Mutationsd. Synonymous (Silent) MutationsIV. Appearance of Most MutationsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.V. Amounts of Mutations/ Mutation RatesVI. How Do Mutations Affect Hardy-Weinberg Equilibrium?VII. How to Measure Mutation Ratesa. Indirect b. DirectVIII. Mutations in Eggs vs. SpermIX. Mutation SummaryOutline of Current Lecture Population Genetics (drift)I. Mutation Rates Vary in Sperm vs. Eggs (sex-dependent)II. Mutation SummaryIII. Hardy-Weinberg (H-W) Assumptions- Random Mating- No Mutation- Infinite Population Size- No Natural Selection- No Migration (no gene flow)IV. Genetic Drif- Sampling Error- Two Primary Population Genetic EffectsV. Genetic Drif in ActionVI. Change in Allele Frequencies by Drif- Small Population Size on Genetic DrifVII. Effective Population Size (Ne)VIII. Inbreeding Current LecturePopulation Genetics (drift)I. Mutation Rates Vary in Sperm vs. Eggs (sex-dependent)- Mutation rate higher in sperm because undergo many more meiotic and mitotic divisions= 380 divisions by 30 years so have lots more opportunities for error to occur - Female eggs only undergo 24 cell divisionsII. Mutation Summary- Mutation common on a per gamete (or per genome) basis, but rare per gene- Many mutations in Eukaryotes neutral or nearly so- Majority mutations with phenotypic effects are deleterious (bad) and recessive (hidden)- Mutation alone has little effect on HW equilibrium, but provides ultimate raw material for evolution- Mutation rates may be affected by sex, and other factors.III. Hardy-Weinberg (H-W) Assumptions- Random Mating- No Mutation- Infinite Population Size- No Natural Selection- No Migration (no gene flow)IV. Genetic Drif: random changes in allele frequencies in populations from one generation to the next, due to chance sampling error. p & q in the next generation (g+1) DO NOT represent what they were in the current generation g, due to chance sampling events- RESULTS FROM RANDOM SAMPLING ERROR- Sampling Error: higher with smaller sample- Two Primary Population Genetic Effects:i. Change in allele frequenciesii. Loss of genetic variation (loss of heterozygosity)** The smaller the population size (N), the greater the changes in 1 & 2 will be**V. Genetic Drif in Action: Peter Buri (1956)- In flies, eye color influenced by the bw locus:ww/bw = whitebw/bw75= orangebw75/bw75= redBuri stated 107 populations of 16 flies each:-8males, 8 females, all heterozygotes (bw/bw75)-Allowed to reproduce-Each generation, 8m and 8f selected for next gen.-Repeated 19 generationsVI. Change in Allele Frequencies by Drif- The direction of change is random, and cannot be predicted.- The magnitude (amount) of change can be predicted and depends on population size.- 95% of the time the allele frequency in next generation, g +1, will be in the interval:p’= p (+ or – )2 Square root ((pq)/(2N))- If N=10:p=freq(A1)= 0.6p'= 0.6 (+ or -) 2 (0.11)= 0.6 (+ or -) 0.2295% of the time, p’ will be between 0.38 and 0.82 ** look at chart on powerpoint slides- If N=10095% of the time p’ will be between 0.67 and 0.53*** Drif is stronger in smaller populations- Small Population Size on Genetic Drif: drif increases with smaller populationsi. The more unpredictable the change in frequenciesii. The more likely one allele will be lost (and the other will be fixed).iii. The more rapidly heterozygosity is eliminated from the population (H declines).- How large is large enough?i. In real populations, the actual rate of loss of genetic variation (heterozygosity) may be much greater than expected given the census sizeii. Many individuals may not reproduce for various reasons. Or some individuals may be much more successful at reproducing than others.VII. Effective Population Size (Ne): size of the ideal population (N) that will result in the same amount of genetic drif (rate of loss of heterozygosity) as in the actual population being considered.- Census Populations DOES NOT equal reproducing populationsNe= (4Nf Nm) / (Nf + Nm)Nf=# femalesNm= #males- Strongly influenced by the rarer of the two sexesVIII. Inbreeding: mating between relatives- Occurs more in small populations- Has direct negative effects on fitness (inbreeding depression) by increasing homozygosity of harmful recessive alleles- Leads to a loss of genetic diversity and less opportunity for adaptive


View Full Document

UM BIOB 272 - Populations Genetics (drift) Day 2

Type: Lecture Note
Pages: 6
Documents in this Course
Load more
Download Populations Genetics (drift) Day 2
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Populations Genetics (drift) Day 2 and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Populations Genetics (drift) Day 2 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?