Name: _______________________________
Genetics 314 – Spring, 2006
Exam 4 – 100 points
Part 1 – 82 points: Answer all questions
1. What are Mendel’s two laws and how do they relate to events in meiosis?
2. You are studying six traits in a plant and all six traits are on different chromosomes.
You mate the following genotypes:
Aa DD Ee Ff gg Ll x Aa Dd Ee Ff Gg Ll
Out of 3000 progeny how many of the following genotypes would you expect to
recover?
1)
2)
3)
4)
AA DD EE FF Gg LL
Aa Dd Ee Ff Gg Ll
aa dd ee ff gg ll
aa Dd Ee ff Gg Ll
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Name: _______________________________
3. Since you recently finished a degree at the University of Idaho that required a genetics
class, you are asked by some recently married members of your extended family if
you could help them determine the odds of having certain combinations of kids. If
the couples want to have 7 children, calculate the probabilities for the following
combinations:
a)
b)
c)
d)
6 boys – 1 girl
4 boys – 3 girls
2 boys – 5 girls
0 boys – 7 girls
4. If someone said they wanted their children in a specific order (boy – girl – boy – girl –
boy – girl – boy) would the probability change from what you calculated for 3b?
Briefly explain your answer.
5. You are studying coat color in rabbits and are told that there are 6 alleles for coat
color.
a) With six alleles how many genotypes would you have if five of the alleles were
codominant and one was recessive?
b) Would you expect the same number of phenotypes as genotypes? Briefly explain
your answer.
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Name: _______________________________
6. You are asked to look at some concordance data on twins to determine which traits are
under more genetic control and which are under more environmental control. You
are given the following data:
trait
depression
high blood pressure
dependability
leadership skills
cholesterol level
identical twins
78%
65%
85%
70%
68%
fraternal twins
40%
30%
83%
67%
25%
a) Which traits are under more genetic control?
b) Which traits are under more environmental control?
c) Why would some traits under more genetic control have a relatively low level of
concordance in identical twins?
7. You are studying the expression of coat color in animals and observe a genotype in the
F1 you have never observed before. Suspecting you are observing epistasis you mate
the F1 and observe the following progeny:
phenotype
dark brown
light brown
white
total
number
103
77
14
194
a) What type of gene action are you observing?
b) Test your hypothesis using Chi square analysis (please show your work).
.
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Name: _______________________________
8. Working with fruit flies you study three genes that you think are on the same
chromosome. The traits are long wing (L – long, l – normal), big abdomen ( B – big,
b – normal) and flying speed (N – normal, n – slow). You cross true breeding parents
to produce F1 progeny that are completely heterozygous for the traits. You mate the
F1 flies with a homozygous recessive flies (ll bb nn) and recover the following F2
progeny:
genotype
number
L b n
l B N
2,250
2,275
L B n
l b N
280
310
L b N
l B n
155
165
l b n
L B N
8
7
total
5450
a) What were the genotypes of the true breeding parents?
b) What is the gene order?
c) Draw a gene map of the three genes showing the genetic distance between the
genes.
d) What is the interference value for these genes?
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Name: _______________________________
Part 2. - 18 points: Answer 3 of the following 4 questions
9. You are observing a trait in cattle and discover an odd inheritance pattern. The trait
will appear in both male and female progeny if the father expresses the trait. If the
mother is the parent expressing the trait, neither male nor female progeny will express
the trait. You determine using molecular markers that the gene for the trait is not on
the sex chromosome. What recently discovered (past 5 years or so) genetic
phenomenon could explain this type of inheritance pattern? Briefly explain your
answer.
10. You are studying wing shape (curled) in fruit flies and you notice you are getting odd
results for the trait that you believe is under the control of a single gene. When you
mate a curled wing fly with a normal wing fly you get a 1 : 1 ratio of curled to normal
winged progeny. When you mate two curled winged flies you get segregation of
progeny with more of the progeny having curled wings than normal wings. No
matter how many curled winged flies you mate you always get progeny that segregate
for curled and normal wings. What type of gene action is occurring here and briefly
explain your answer.
11. You are told a trait you are studying is a recessive sex-linked trait. What type of
cross or crosses would you make to test this hypothesis and what progeny would you
expect from this cross or crosses if the trait was indeed a recessive sex-linked trait?
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Name: _______________________________
12. What are the differences between a trait under qualitative genetic control and a trait
under quantitative genetic control?
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