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Lecture 16 – February 22, 2010
Review For Midterm Exam
Question 1
Genotype
BB
Bb
bb
Number
22
16
6
44
a) What are allele frequencies?
p(B) = (22 + 8)/44 = .68
Question 1
Genotype
BB
Bb
bb
Number
22
16
6
44
b) Expected numbers for genotypes?
p(BB) = .68 x .68 x 44 = 20.34
p(Bb) = 2 x .68 x .32 x 44 = 19.15
p(bb) = .32 x .32 x 44 = 4.51
Question 1
Genotype
BB
Bb
bb
Number
22
16
6
44
Expected
20.34
19.15
4.51
b) HWE?
LR = -2[ 22 ln(20.34/22) + 16 ln(19.15/16) +
6 ln(4.51/6) ]
= 1.1266 with 1 df < 3.84 = NS
Question 2
About 4% of people express an autosomal
recessive genotype.
What is the frequency of the recessive allele?
q = sqrt(.04) = .2
What percentage of people would be
heterozygous?
2 p q = 2 (.2)(.8) = .32 OR 32%
Question 2
About 32% of people express a heterozygous
genotype for some locus.
What is the frequency of the recessive allele?
2 p q = .32
p ( 1-p ) = .16
-p(p) + p -.16 = 0 (quadratic equation)
a = -1, b = 1, c = -.16
p = [-1 +/- sqrt( b x b – 4 a c ) ]/ 2 a
= -.2 or .8 (take positive result)
q = 1 - .8 = .2
Question 3
Assume a sex linked locus with 4 alleles,
Females, p1=.1, p2=.2, p3=.3, and p4=.4
Males, p1=.5, p2=.3, p3=.2, and p4=0
What are the expected progeny genotypes?
.1
.2
.3
.4
.5
.3
.2
.05 11
.03 12
.02 13
Males .1 1Y
.10 12
.06 22
.04 23
.15 13
.09 23
.06 33
.20 14
.12 24
.08 34
.2 2Y
.3 3Y
.4 4Y
Question 3
.1
.5
.3
.2
.05 11
.03 12
.02 13
.2
.10 12
.06 22
.04 23
.3
.15 13
.09 23
.06 33
Males .1 1Y
.2 2Y
.3 3Y
What are new allele frequencies?
.4
.20 14
.12 24
.08 34
.4 4Y
Females, p1 = (.05 + .5(.10+.15+.20+.03+.02))= .3
p2 = .25, p3 = .25, p4=.2
Males, p1 = .1, p2=.2, p3=.3, p4=.4
Question 4
Genotype
GG
Gg
gg
Freq. v(ij)
.04
8
.32
-4
.64
-6
What type of gene action is this?
What is the mean?
mean = .04(8) - .32(4) - .64(6) = -4.8
What are the allelic effects?
a(G) = 3.2
a(g) = -0.8
Question 4
Genotype Freq. v(ij)
GG
.04
8
Gg
.32
-4
gg
.64
-6
mean = -4.8
a(G) = 3.2
a(g) = -0.8
D(GG) = 8 – mean – 2 a(G) = 6.4
D(Gg) = -4 – (-4.8) - a(G) - a(g) = -1.6
D(gg) = .4
Question 4
Genotype
GG
Gg
gg
Freq. v(ij)
.04
8
.32
-4
.64
-6
A(ij)
6.4
2.4
-1.6
D(ij)
6.4
-1.6
.4
Var(A) = .04(40.96) + .32(5.76) + .64(2.56) = 5.12
Var(D) = .04(40.96) + .32(2.56) + .64(.16) = 2.56
Question 5
Number of matings to detect carriers, if
matings to carriers, or to general population.
Question 6
Migration, mixing of populations with different
allele frequencies – new frequencies.
Question 6b
Two loci, UNLINKED, expected frequencies of
gametes.
A
A
a
a
B
b
B
b
=
=
=
=
p(A) x p(B)
p(A) x p(b)
p(a) x p(B)
p(a) x p(b)
Linkage disequilibrium = gametic phase
disequilibrium
Question 7
Two loci, LINKED, expected frequencies of gametes.
A
A
a
a
B =
b =
B =
b =
.5 (1 - r(AB))
.5 r(AB)
.5 r(AB)
.5 (1 – r(AB))
Haldane mapping function
Kosambi mapping function
Question 8
Loci interactions
additive
dominance
add by add
dom by dom
add by dom
add by add by add
add by dom by dom
add by add by dom, etc.
Question 9
Linkage disequilibrium, between linked loci or
unlinked loci.
LD(n) = (1 – r)n LD(0)
If LD(0) = .24, and LD(3) = .12, what is r ?
.12 = ( 1 – r )3(.24), solve for r
Question 10
Three loci, estimate recombination rates
between each pair.
What is the crossover interference?
Question 11
Path coefficient method,
Determining the covariance between variables,
and inbreeding coefficients.
Tabular Method of computing relationships.
Wright’s relationship coefficient versus
a(i,j), range of values.
A
B
C
D
E
F
G
L
Q
H
M
R
Cov(P,Q) = ??
J
I
O
N
S
K
T
P
What was the error on page 3 of
section 3.3 of notes?
What are the colour genotypes of
Prof’s two yellow labrador
retrievers?
What is the map distance between
Guelph and Vancouver in Morgans?
Who hit the most home runs in their
career in professional baseball? (868)
Who was the greatest cricket player in
Australian history?
What race horse was mentioned in
class? (not Seabiscuit)
Why was Sewall Wright unable to buy
life insurance?
Mid term Exam
February 24, 2010
Rozanski 104, 4:30 PM
I will be in Axelrod 200 at
3:30 pm to help anyone