Lecture 2

Question 1

Local/ Mendelian populations

Answer 1

interbreeding units, often geographically defined

• empirically verified
• genetic pops reflect a group of individuals that are genetically more closely related to each other than to individuals outside group.

Question 2

Genotype Freqs

Answer 2

• common goal= use allele freqs to predict genotypes o population (=1).
• different genotype distrs are consistent w/ any set o allele freqs
• prediction model= random union of gametes.
• p2+2pq+q2=1

Question 3

Hardy-Weinberg Equilibrium- conditions

Answer 3

states that genotype freqs o population remain constant fr/ gen to gen.  
-disturbing influs introd=
Non-random mating 
Finite population size (genetic drift) 
Mutation 
Gene flow 
NSel

Question 4

Calc HWE

Answer 4

Calc expected genos» compare w/ obs freqs

Question 5

Degrees of Freedom

Answer 5

“# of independent obs”

Question 6

Implications o HWE- maintenance o allele freqs

Answer 6

genetic vari w/in pop not blended away over successive generations

Question 7

Implications o HWE- changes of allele freqs

Answer 7

conditions o HW are not met= new muts, genetic drift, gene flow, + NSel
-assorted matg not change allele freqs

Question 8

Study assumptions

Answer 8

How sampled (rep?, mo than 1 region rep?)

• genotyping mistakes (heteros easily mistaken as homos)
• Type I error (chance deviation, sig level» false pos result)

Question 9

Finite Pops

Answer 9

• Genetic drift (sampling) w/out replacement

- calcs always have mo heteros (lrgr sample= less pronounced)

Question 10

Sex Diffs in Allele Freqs

Answer 10

mo heteros in offspring b/c allele freqs o men+ wmn differ in prnt pop

Question 11

X-Linked Loci

Answer 11

• total allele freq= average o 1 part male freqs+ 2 parts female freqs
• shld not deviate fr/ HWE
• diff allele freqs reduced by 1/2 ea. gen= rapid equil

Question 12

Multi Loci- haplotype

Answer 12

• all possible gamete types
• 2 genes on same/diff chromos
• allele freqs inferred fr/ haplotype freqs
• haplotype freqs not inferred fr/ allele freqs
• can change b/w gens

Question 13

Multi Loci- Linkage Disequil

Answer 13

• non-random assctn o alleles at diff loci (D= non-zero» hap @ 1 loci give info on allele carried by hap @ other locus)
• mo space b/w loci= mo opp fo recombinations
• D= non-recomb - recombs= funct o haplotype freqs

Question 14

LD sources

Answer 14

Positive Selection
Neg selection
Sel/ hitchhiking sweeps
genetic drift 
pop admixture

Question 15

LD sources- Positive selection

Answer 15

where sel favors fixation o an allele or trait that increases fitness o carrier.

Question 16

LD sources- Sel/ hitchhiking sweeps

Answer 16

close assoctn/ physically close» carried w/ pos selc

Question 17

LD sources- Neg sel

Answer 17

where sel removes fixation o an allele or trait that decreases fitness o carrier

Question 18

LD sources- Genetic Drift

Answer 18

random sampling reduced b/c o founder effect or bottleneck

Question 19

LD sources- Pop admixture

Answer 19

gene flow= intro new/ favored alleles