Upload
rosalyn-conley
View
36
Download
3
Embed Size (px)
DESCRIPTION
Measuring Evolution of Populations. 5 Agents of evolutionary change. Mutation. Gene Flow. Non-random mating. Genetic Drift. Selection. Populations & gene pools. Concepts a population is a localized group of interbreeding individuals - PowerPoint PPT Presentation
Citation preview
AP Biology 2007-2008
MeasuringEvolution of Populations
AP Biology
5 Agents of evolutionary changeMutation Gene Flow
Genetic Drift Selection
Non-random mating
AP Biology
Populations & gene pools Concepts
a population is a localized group of interbreeding individuals
gene pool is collection of alleles in the population remember difference between alleles & genes!
allele frequency is how common is that allele in the population how many A vs. a in whole population
AP Biology
Evolution of populations Evolution = change in allele frequencies
in a population hypothetical: what conditions would
cause allele frequencies to not change? non-evolving population
REMOVE all agents of evolutionary change
1. very large population size (no genetic drift)
2. no migration (no gene flow in or out)
3. no mutation (no genetic change)
4. random mating (no sexual selection)
5. no natural selection (everyone is equally fit)
AP Biology
Hardy-Weinberg equilibrium Hypothetical, non-evolving population
preserves allele frequencies
Serves as a model (null hypothesis) natural populations rarely in H-W equilibrium useful model to measure if forces are acting
on a population measuring evolutionary change
W. Weinbergphysician
G.H. Hardymathematician
AP Biology
Hardy-Weinberg theorem Counting Alleles
assume 2 alleles = B, b frequency of dominant allele (B) = p frequency of recessive allele (b) = q
frequencies must add to 1 (100%), so:
p + q = 1
bbBbBB
AP Biology
Hardy-Weinberg theorem Counting Individuals
frequency of homozygous dominant: p x p = p2 frequency of homozygous recessive: q x q = q2 frequency of heterozygotes: (p x q) + (q x p) = 2pq
frequencies of all individuals must add to 1 (100%), so:
p2 + 2pq + q2 = 1
bbBbBB
AP Biology
H-W formulas Alleles: p + q = 1
Individuals: p2 + 2pq + q2 = 1
bbBbBB
BB
B b
Bb bb
AP BiologyWhat are the genotype frequencies?What are the genotype frequencies?
Using Hardy-Weinberg equation
q2 (bb): 16/100 = .16
q (b): √.16 = 0.40.4
p (B): 1 - 0.4 = 0.60.6
q2 (bb): 16/100 = .16
q (b): √.16 = 0.40.4
p (B): 1 - 0.4 = 0.60.6
population: 100 cats84 black, 16 whiteHow many of each genotype?
population: 100 cats84 black, 16 whiteHow many of each genotype?
bbBbBB
p2=.36p2=.36 2pq=.482pq=.48 q2=.16q2=.16
Must assume population is in H-W equilibrium!
Must assume population is in H-W equilibrium!
AP Biology
Using Hardy-Weinberg equation
bbBbBB
p2=.36p2=.36 2pq=.482pq=.48 q2=.16q2=.16
Assuming H-W equilibriumAssuming H-W equilibrium
Sampled data Sampled data bbBbBB
p2=.74p2=.74 2pq=.102pq=.10 q2=.16q2=.16
How do you explain the data? How do you explain the data?
p2=.20p2=.20 2pq=.642pq=.64 q2=.16q2=.16
How do you explain the data? How do you explain the data?
Null hypothesis Null hypothesis
AP Biology
Application of H-W principle Sickle cell anemia
inherit a mutation in gene coding for hemoglobin oxygen-carrying blood protein recessive allele = HsHs
normal allele = Hb
low oxygen levels causes RBC to sickle breakdown of RBC clogging small blood vessels damage to organs
often lethal
AP Biology
Sickle cell frequency High frequency of heterozygotes
1 in 5 in Central Africans = HbHs
unusual for allele with severe detrimental effects in homozygotes 1 in 100 = HsHs
usually die before reproductive age
Why is the Hs allele maintained at such high levels in African populations?Why is the Hs allele maintained at such high levels in African populations?
Suggests some selective advantage of being heterozygous…Suggests some selective advantage of being heterozygous…
AP Biology
Malaria Single-celled eukaryote parasite (Plasmodium) spends part of its life cycle in red blood cells
Single-celled eukaryote parasite (Plasmodium) spends part of its life cycle in red blood cells
1
2
3
AP Biology
Heterozygote Advantage In tropical Africa, where malaria is common:
homozygous dominant (normal) die or reduced reproduction from malaria: HbHb
homozygous recessive die or reduced reproduction from sickle cell anemia: HsHs
heterozygote carriers are relatively free of both: HbHs
survive & reproduce more, more common in population
Hypothesis:In malaria-infected cells, the O2 level is lowered enough to cause sickling which kills the cell & destroys the parasite.
Hypothesis:In malaria-infected cells, the O2 level is lowered enough to cause sickling which kills the cell & destroys the parasite. Frequency of sickle cell allele &
distribution of malaria
AP Biology 2005-2006
Any Questions??Any Questions??Any Questions??
AP Biology 2006-2007
Hardy-WeinbergLab Data
Mutation Gene Flow Genetic Drift Selection Non-random mating
AP Biology
Hardy Weinberg Lab: Equilibrium
total alleles = 36
p (A): (4+4+7)/36 = .42.42
q (a): (7+7+7)/36 = .58.58
total alleles = 36
p (A): (4+4+7)/36 = .42.42
q (a): (7+7+7)/36 = .58.58
18 individuals
36 alleles
p (A): 0.50.5
q (a): 0.50.5
18 individuals
36 alleles
p (A): 0.50.5
q (a): 0.50.5
Original populationOriginal population
AA44
Aa77
aa77
How do you explain these data? How do you explain these data?
Case #1 F5Case #1 F5
AA.25.25
Aa.50.50
aa.25.25
AA.22.22
Aa.39.39
aa.39.39
AP Biology
Hardy Weinberg Lab: Selection
total alleles = 30
p (A): (9+9+6)/30 = .80.80
q (a): (0+0+6)/30 = .20.20
total alleles = 30
p (A): (9+9+6)/30 = .80.80
q (a): (0+0+6)/30 = .20.20
15 individuals
30 alleles
p (A): 0.50.5
q (a): 0.50.5
15 individuals
30 alleles
p (A): 0.50.5
q (a): 0.50.5
Original populationOriginal population
AA99
Aa66
aa00
How do you explain these data? How do you explain these data?
Case #2 F5Case #2 F5
AA.25.25
Aa.50.50
aa.25.25
AA.60.60
Aa.40.40
aa00
AP Biology
Hardy Weinberg Lab:
total alleles = 30
p (A): (4+4+11)/30 = .63.63
q (a): (0+0+11)/30 = .37.37
total alleles = 30
p (A): (4+4+11)/30 = .63.63
q (a): (0+0+11)/30 = .37.37
15 individuals
30 alleles
p (A): 0.50.5
q (a): 0.50.5
15 individuals
30 alleles
p (A): 0.50.5
q (a): 0.50.5
Original populationOriginal population
AA44
Aa1111
aa00
How do you explain these data? How do you explain these data?
Case #3 F5Case #3 F5
AA.25.25
Aa.50.50
aa.25.25
AA.27.27
Aa.73.73
aa00
Heterozygote Advantage
AP Biology
Hardy Weinberg Lab:
total alleles = 30p (A): (6+6+9)/30 = .70.70
q (a): (0+0+9)/30 = .30.30
total alleles = 30p (A): (6+6+9)/30 = .70.70
q (a): (0+0+9)/30 = .30.30
15 individuals
30 alleles
p (A): 0.50.5
q (a): 0.50.5
15 individuals
30 alleles
p (A): 0.50.5
q (a): 0.50.5
Original populationOriginal population
AA66
Aa99
aa00
How do you explain these data? How do you explain these data?
Case #3 F10Case #3 F10
AA.25.25
Aa.50.50
aa.25.25
AA.4.4
Aa.6.6
aa00
Heterozygote Advantage
AP Biology
Hardy Weinberg Lab: Genetic Drift
total alleles = 12
p (A): (4+4+2)/12 = .83.83
q (a): (0+0+2)/12 = .17.17
total alleles = 12
p (A): (4+4+2)/12 = .83.83
q (a): (0+0+2)/12 = .17.17
6 individuals
12 alleles
p (A): 0.50.5
q (a): 0.50.5
6 individuals
12 alleles
p (A): 0.50.5
q (a): 0.50.5
Original populationOriginal population
AA44
Aa22
aa00
How do you explain these data? How do you explain these data?
Case #4 F5-1Case #4 F5-1
AA.25.25
Aa.50.50
aa.25.25
AA.67.67
Aa.33.33
aa00
AP Biology
Hardy Weinberg Lab: Genetic Drift
total alleles = 10
p (A): (0+0+4)/10 = .4.4
q (a): (1+1+4)/10 = .6.6
total alleles = 10
p (A): (0+0+4)/10 = .4.4
q (a): (1+1+4)/10 = .6.6
5 individuals
10 alleles
p (A): 0.50.5
q (a): 0.50.5
5 individuals
10 alleles
p (A): 0.50.5
q (a): 0.50.5
Original populationOriginal population
AA00
Aa44
aa11
How do you explain these data? How do you explain these data?
Case #4 F5-2Case #4 F5-2
AA.25.25
Aa.50.50
aa.25.25
AA00
Aa.8.8
aa.2.2
AP Biology
Hardy Weinberg Lab: Genetic Drift
total alleles = 10
p (A): (2+2+2)/10 = .6.6
q (a): (1+1+2)/10 = .4.4
total alleles = 10
p (A): (2+2+2)/10 = .6.6
q (a): (1+1+2)/10 = .4.4
5 individuals
10 alleles
p (A): 0.50.5
q (a): 0.50.5
5 individuals
10 alleles
p (A): 0.50.5
q (a): 0.50.5
Original populationOriginal population
AA22
Aa22
aa11
How do you explain these data? How do you explain these data?
Case #4 F5-3Case #4 F5-3
AA.25.25
Aa.50.50
aa.25.25
AA.4.4
Aa.4.4
aa.2.2
AP Biology
Hardy Weinberg Lab: Genetic Drift
5 individuals
10 alleles
p (A): 0.50.5
q (a): 0.50.5
5 individuals
10 alleles
p (A): 0.50.5
q (a): 0.50.5
Original populationOriginal population
AA Aa aa p q
1 .67.67 .33.33 00 .83.83 .17.17
2 00 .8.8 .2.2 .4.4 .6.6
3 44 .4.4 .2.2 .6.6 .4.4
How do you explain these data? How do you explain these data?
Case #4 F5Case #4 F5
AA.25.25
Aa.50.50
aa.25.25
AP Biology 2007-2008
Any Questions??