Download population genetics multiple

Population Genetics
Multiple Alleles
Population Genetics
Aa
AA
• Study of genetic
variation in
populations.
aa
• Genotype
Aa
AA
Aa
frequencies • Allele frequencies
Aa
Aa
AA
aa
Summary of Frequencies
Allele
GenoGenotype
Genotype
Alleles
Freq.
types
Freq.
Freq. if H-W
A
a
p
q
Always:
p = P+1/2 H
q = Q+1/2 H
AA
P
p2
Aa
H
2pq
aa
Q
q2
ONLY if H-W:
q = √q2 = √Q
p = 1-q
Hardy-Weinberg
Equilibrium
• Genotype and allele frequencies remain
constant from one generation to the next if:
• random mating
• no migration
• no mutation
• no natural selection
• large population size
Codominace
Phenotype Genotype
Number
Frequency
Freckled
FF
38
0.38 =P
Freckled,
Spotted
FS
44
0.44 =H
Spotted
SS
18
0.18 =Q
Total
p = P + 1/2 H
q = Q + 1/2 H
100
1
p = 0.38 + 1/2 (0.44) =0.6
q = 0.18 + 1/2 (0.44) = 0.4
Complete Dominance
Phenotype
Phenotype Number
Genotype
Frequency
Black
112
0.84
AA
Aa
Gray
21
0.16
aa
Total
133
1
Genotype
Frequency
P=p2=0.36
H=2pq=0.48
Q=0.16
Q = q2 = proportion of aa = 0.16
q = √0.16 = 0.4
p=1-q = 0.6
1
Multiple Alleles
more than 2 alleles for trait
e.g. ABO Blood Types
Genotypes Phenotypes
AA
Type A
Ai
BB
Type B
Bi
AB
Type AB
ii
Type O
Alleles: A, B, i
p = freq A
q = freq B
r = freq i
Multiple Alleles
A
p
A
p
p2
Alleles: A, B, i
B
i
q
r
pq
B
q
pq
q2
i
r
pr
qr
pr
qr
r2
p = freq A
q = freq B
r = freq i
p2 = freq. AA
2pq = freq. AB
q2 = freq. BB
2pr = freq. Ai
2qr = freq. Bi
r2 = freq. ii
Multiple Alleles
Phenotypes
Freq.
Type A
0.41
Type B
0.09
Type AB
Type O
0.03
0.47
Genotypes If H-W
AA
p2+ 2pr
Ai
BB
q2 +2qr
Bi
AB
2pq
ii
r2
Multiple Alleles
2 + 2pr
p
Freq. Type A = 0.41
Freq. Type B = 0.09 q2 + 2qr
Freq. Type AB = 0.03 2pq
Freq. Type 0 = 0.47
r2
r2 = freq. ii = 0.47
r = √r2 = 0.69
(p + r)2 = p2 + 2pr + r2
√(p + r)2 = √(p2 + 2pr + r2)
p + r = √(p2 + 2pr + r2)
p = √(p2 + 2pr + r2) - r
p = √(0.41 + 0.47) - 0.69
p = 0.25
p+q+r=1
q =1 - p - r
q=1-0.25-0.47=0.06
Multiple Alleles
Alleles: A, B, i
Freq. Type A = 0.41
p = freq A
Freq. Type B = 0.09
q = freq B
Freq. Type AB = 0.03
r = freq i
Freq. Type 0 = 0.47
0.25
0.06
0.69
(0.25)2 = 0.0625
p2 = freq. AA
2pq = freq. AB 2(0.25) (0.06) = 0.03
(0.06)2 = 0.0036
q2 = freq. BB
2pr = freq. Ai
2(0.25) (0.69) = 0.34
2qr = freq. Bi
2(0.06) (0.69) = 0.083
r2 = freq. ii
0.47
Lab 14
• Gather info on taste and blood type
• Calculate population genetics
• Get info on population genetics for your
project
• Sample Presentation
Fabry Disease
Genetics
Fabry Disease Symptoms
Pain – full body or localized in extremities or GI
Kidney problems —> Renal failure
Heart disease and hypertension
Clouding of cornea
Fatigue, vertigo, nausea
Decreased ability to sweat
Skin papules in buttocks, thighs, groin, lower
abdomen
Inheritance
GLA (galactosidase, alpha) gene!
X-linked recessive!
Heterozygous females do show some symptoms
X Chromosome
q arm!
Xq22.2
Molecular
globotriaosylceramide
(fatty substance)
breakdown products
Alpha Galactosidase
GLA gene codes for alpha galactosidase !
GLA - 1290 bp’s with 7 exons!
370 mutations - many are point, missense mutations,
some frameshift!
Accumulation of glycolipids in blood vessels impairs
function
Population Genetics
frequency males 1/50,000 Thus q = .00002 and p = .99998
US census – there are about 3,800 males with
Fabry in U.S. Based on HW there are about 7,600 females
that carry the Fabry gene but an unknown
number of females affected (having significant
symptoms) by the disease.