CSS 650 Advanced Plant Breeding
Midterm 2011
Name
Please show your work.
1) A single recessive gene in meadowfoam causes flower buds to be glabrous (no pubescence).
The species is normally cross-pollinated by honey bees. On a vacation to Salt Spring Island
in British Colombia, a plant breeder discovers an isolated population of meadowfoam and
observes that the frequency of glabrous plants is 0.16.
8 pts
a) If the population is in Hardy-Weinberg Equilibrium, what is the expected frequency of
plants that are homozygous for the dominant allele?
8 pts
b) She selected 50 pubescent plants and crossed all of them to glabrous plants. How many of
the 50 pubescent plants would you expect to produce progeny that are segregating for the
pubescent/glabrous trait?
2) In a new synthetic variety of corn, the frequency of an allele ‘A’ is 0.6, and the frequency of
allele ‘B’ at another locus is 0.6. The frequency of ‘AB’ gametes in the current generation is
0.55.
6 pts
a) What is the value of D (the disequilibrium coefficient) in this generation?
8 pts
b) Under ideal conditions, the disequilibrium will be reduced by one-half in each subsequent
generation. Name two factors that could slow down the rate of decay of disequilibrium
between these two loci.
1
6 pts
3) You have been given 10 corn kernels from a very large, random-mating population. You
plant the corn in your garden. You are the only person in your neighborhood growing corn.
What is the expected level of inbreeding after one generation of random mating?
4) Assume that the parents in the mating scheme below are not inbred.
C
A
B
D
E
X
8 pts
a) What is the inbreeding coefficient of Y?
10 pts
b) What is the coancestry of X and Y?
Y
2
5) A random-mating population of corn is segregating at the ‘A’ locus, which determines days
to flowering. The table below shows the frequency of genotypes and their observed
genotypic values.
a) Fill in the coded values for these genotypes.
Frequency
Value
A1A1
0.36
58
A1A2
0.48
55
A2A2
0.16
50
8 pts
Coded
8 pts
b) Calculate the population mean on the original scale.
8 pts
c) If you cross an A1A1 genotype with an A2A2 genotype, what is the expected breeding
value of the progeny (in reference to the original random-mating population)?
8 pts
d) What is the additive genetic variance for this locus?
3
6 pts
6) Consider the graph below showing the regression of genotypic values on number of
favorable Z1 alleles:
genotypic value
genotypic value

0
Z2Z2
1
Z1Z2
2
Z1Z1
The variance among genotypic values = 12 and the variance due to linear regression = 8.
What is the estimate of dominance variance?
8 pts
7) A nature lover has been visiting a national park every summer for the past ten years. He has
noticed that the frequency of a purple form of his favorite wildflower has increased steadily
over the years, while the pink form has become less prevalent. What possible explanations
could you provide for the changes that he has observed?
4
Extra Credit
6 pts
1) A fellow graduate student sees that you are hard at work using the tabular method to estimate
coancestries for a complex pedigree. He suggests that you should use a popular software
package to solve the problem instead. He runs the kinship program and obtains the following
output:
indiv parent1 parent2
A
B
C
D
E
G
H
X
A
A
B
A
D
G
B
B
C
E
H
A
B
C
D
E
G
H
X
1.0000
.
0.5000
0.5000
.
0.7500
0.2500
0.5000
.
1.0000
0.5000
0.5000
0.5000
0.2500
0.5000
0.3750
0.5000
0.5000
1.0000
0.5000
0.2500
0.7500
0.3750
0.5625
0.5000
0.5000
0.5000
1.0000
0.2500
0.5000
0.6250
0.5625
.
0.5000
0.2500
0.2500
1.0000
0.1250
0.6250
0.3750
0.7500
0.2500
0.7500
0.5000
0.1250
1.2500
0.3125
0.7813
0.2500
0.5000
0.3750
0.6250
0.6250
0.3125
1.1250
0.7188
0.5000
0.3750
0.5625
0.5625
0.3750
0.7813
0.7188
1.1563
Does this appear to be a table of coancestries? What is your evidence?
8 pts
2) Given the formulas for breeding values in the table below, use algebra to show that the
variance of breeding values = 2pqα2 (you can assume that the mean of breeding values is
zero).
Genotype
Frequency
Breeding Value
A1A1
p2
2q
A1A2
2pq
(q - p)
A2A2
q2
-2p
5