Transcript popgen

Population Genetics
Ch. 23 and Beyond; Lab/Lecture Same
Math Calisthenics I
Ladybug Population
Generation One
Calculate TOTAL # A
AA = 200
Aa = 100
aa = 200
Calculate Total # a
Math Calisthenics I
Ladybug Population
Generation One
Calculate TOTAL # A
(200 X 2) + (100 X 1)
Total A = 500
AA = 200
Aa = 100
aa = 200
Calculate Total # a
(200 X 2) + (100 X 1)
Total a = 500
Calculate TOTAL # A
(200 X 2) + (100 X 1)
Total A = 500
Convert to % A
Calculate Total # a
(200 X 2) + (100 X 1)
Total a = 500
Convert to % a
Calculate TOTAL # A
(200 X 2) + (100 X 1)
Total A = 500
Convert to % A
500/1000 = 0.5
(AVOID USING 50%)
Calculate Total # a
(200 X 2) + (100 X 1)
Total a = 500
Convert to % a
500/1000 = 0.5
(AVOID USING 50%)
Ladybug Population
Generation Two
Calculate TOTAL # A
AA = 300
Aa = 100
aa = 100
Calculate Total # a
Ladybug Population
Generation Two
Calculate TOTAL # A
(300 X 2) + (100 X 1)
Total A = 700
AA = 300
Aa = 100
aa = 100
Calculate Total # a
(100 X 2) + (100 X 1)
Total a = 300
Calculate TOTAL # A
(300 X 2) + (100 X 1)
Total A = 700
Convert to % A
Calculate Total # a
(100 X 2) + (100 X 1)
Total a = 300
Convert to % a
Calculate TOTAL # A
(300 X 2) + (100 X 1)
Total A = 700
Convert to % A
700/1000 = 0.7
Calculate Total # a
(100 X 2) + (100 X 1)
Total a = 300
Convert to % a
300/1000 = 0.3
In the language of population genetics,
p = % DOMINANT ALLELES
q = % RECESSIVE ALLELES
p
Ladybug
Generation 1
Ladybug
Generation 2
q
In the language of population genetics,
p = % DOMINANT ALLELES
q = % RECESSIVE ALLELES
Ladybug
Generation 1
Ladybug
Generation 2
p
q
0.5
0.5
0.7
0.3
Class brainstorming - what might cause a
shift in allele frequencies (% A/a or p/q)?
Hardy-Weinberg (1908) predicted allele
frequencies would NOT change if…
Hardy-Weinberg (1908) predicted allele
frequencies would NOT change if…
LARGE POPULATION
Genetic Drift: allele % fluctuations due to
TOO SMALL SAMPLE - BOTTLENECK
Hardy-Weinberg (1908) predicted allele
frequencies would NOT change if…
LARGE POPULATION
NO MIGRATION
Hardy-Weinberg (1908) predicted allele
frequencies would NOT change if…
LARGE POPULATION
NO MIGRATION
NO MUTATIONS
Hardy-Weinberg (1908) predicted allele
frequencies would NOT change if…
LARGE POPULATION
NO MIGRATION
NO MUTATIONS
MATING RANDOM
Hardy-Weinberg (1908) predicted allele
frequencies would NOT change if…
LARGE POPULATION
NO MIGRATION
NO MUTATIONS
MATING IS RANDOM
NO SELECTION FOR CERTAIN TRAITS
Predicting and Detecting Variation
For dom/rec traits, which is only genotype
you know for certain based on
phenotype?
HW developed a useful predictive
equation: p2 + 2pq + q2 = 1
Let’s say you want to predict the #
carriers of a new recessive disease allele.
Math Calisthenics II
Epidemiology Data
from Monmouth
aa = 1600/10,000
Calculate p
Calculate q
Calculate p2 & 2pq
Let’s say you want to predict the #
carriers of a new recessive disease allele.
Math Calisthenics II
Epidemiology Data
from Monmouth
aa = 1600/10,000
Calculate p
Calculate q
q2 = 1600/10,000
= 0.16

= 0.4 = q
Calculate p2 & 2pq
Let’s say you want to predict the #
carriers of a new recessive disease allele.
Math Calisthenics II
Epidemiology Data
from Monmouth
aa = 1600/10,000
Calculate p
p + q = 1… SO
1 - 0.4 = p
0.6 = p
Calculate q
q2 = 1600/10,000
= 0.16

= 0.4 = q
Calculate p2 & 2pq
Let’s say you want to predict the #
carriers of a new recessive disease allele.
Math Calisthenics II
Epidemiology Data
from Monmouth
aa = 1600/10,000
Calculate p
p + q = 1… SO
1 - 0.4 = p
0.6 = p
Calculate q
q2 = 1600/10,000
= 0.16

= 0.4 = q
Calculate p2 & 2pq
p2 = (0.6)(0.6) = 0.36
2pq = 2(0.6)(0.4)
= 0.48
Check Work! Does p2 + 2pq + q2 = 1?
What does this data mean???
Lab: Aside from disease/carrier status,
why is knowing heterozygosity important?
Many alleles
display
polymorphisms
detectable at
DNA OR
PROTEIN
LEVEL
Now consider sickle cell polymorphism…
Prokaryotes make protective nucleases
called RESTRICTION ENZYMES (20.1-2)
e.g. DdeI cuts CTTAG - distinguishes
hemoglobin alleles (Fig. 20.9)
In lab, you will explore protein gels of
enzyme complexes to predict genotypes.
Consider that some enzymes are made of
single proteins - MONOMERS
Hom/Dom
Hom/Rec
Het/Dom
1 BAND
1 BAND
2 BANDS
Others are made of multiple proteins e.g. DIMERS, 2 FOLDED CHAINS
Hom/Dom
Hom/Rec
Het/Dom
1 BAND
1 BAND
3 BANDS
Population Genetics and Evolution
Do any populations meet HW conditions?
RARELY AND NOT FOR LONG
Evolution: CHANGES in the genetic
makeup of a population OVER TIME