Name __________________________
BIOLOGY 445
PID ____________________
SAMPLE EXAM 2
SPRING 2011
Put your name at the top of each page. Please read each question carefully before answeringread the instructions. In all answers, be as specific as possible, while respecting the amount of
space allotted for each answer. Sign the honor pledge at the end of the exam.
1.
Fusion of G2 and S cells does not cause any change in the nuclei of either cells. Give an
example (of a molecular nature) that explains why G2 cells cannot go back to the S phase
2. What causes MPF activity to decline at the end of mitosis (1 sentence)?
3. What would happen in a mammalian cell if the expression of the CKI p16 was induced at a
high level in an asynchronously growing population of cells (i.e. cells in all cell cycle
phases)
4. Cdk1 activity is observed only a while after cyclin B protein synthesis began (see below).
Describe briefly two explanations for why such a delay exists
5. If you were to induce the over-expression of a mutant version of cyclin B that cannot be
ubiquitinated in a population of growing yeast cells, what would happen (1 sentence)?
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Name __________________________
PID ____________________
6. Circle True or False regarding the role of the pRb pathway in cancer.
T
F
Loss of E2F1 function can suppress the incidence of cancer in pRb heterozygous
mice
T F
Hyper-phosphorylation of E2F prevents E2F from binding to pRb
T
Retinoblastoma is inherited as a recessive trait, but is dominant at the cellular
F
level
7. What two important properties of the cell cycle were shown by fusing cells in G1 or G2 with
cells in the S phase?
8. How was human cdc2 kinase first isolated?
9. Circle any of the following statements that are consistent with the known action of the S.
pombe wee1 protein (i.e. there could be more than one).
a. phosphorylates cdc2 on Tyr15
b. phosphorylates cdc2 on Thr 161
c. inhibits the kinase activity of cdc2 protein
d. dephosphorylates and activates CAK kinase
e. dephosphorylates Tyr15 of cdc2
10. The restriction point in mammalian cells is equivalent to (circle one):
a. the anaphase stage of M phase
b. START in S. cerevisiae
c. the point at which the spindle forms
d. G2-M control in S. pombe
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Name __________________________
PID ____________________
11. For each of the following situations in S. pombe, indicate whether a “wee” phenotype,
characterized as small cells with a shortened G2 phase, or a G2 arrest phenotype would
occur (write either “wee” or “G2 arrest” on the line provided). For temperature sensitive
alleles (ts), assume the phenotype was scored at the restrictive temperature. L= loss of
function
ts mutation of cdc2
_______________
ts mutation of cdc25
_______________
a wee1 lf mutation
_______________
expression of a cdc2 mutant that
cannot be phosphorylated on Tyr 15 _______________
expression of a cdc2 mutant that
cannot be phosphorylated on Thr 161 _______________
over expression of cdc25
_______________
a dominant, hyperactive cdc2 allele _______________
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Name __________________________
12.
PID ____________________
The next questions refer to a figure (see below) from the MAD2 paper we discussed
a. How were the cells treated to test the timing of metaphase to anaphase transition?
b. What can we conclude from this figure?
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Name __________________________
PID ____________________
13. In the current medical environment retinoblastoma is not usually fatal. Retinoblastoma
cancer patients can therefore have children. The picture below depicts a pedigree of a
retinoblastoma family. In this picture, the filled circles (male) and square (female) indicate
individuals with retinoblastoma. A cancer geneticist collected blood samples from each of
the family members and performed a hybridization experiment on the DNA isolated from
each member’s blood cells with a marker DNA from the Rb locus that can detect three
different alleles designated “a”, “b”, or “c”. The results of these hybridizations are shown
next to each family member in the pedigree.
When the same hybridization experiment is performed with the DNA isolated from the
retinoblastoma the tumors of children #1 and #3, what is the expected result if both children’s
tumors have developed as a result of loss of heterozygosity at the Rb locus? Circle the
correct answer.
a. one single band corresponding to band a
b. two bands corresponding to a and c
c. one single band corresponding to band c
d. two bands corresponding to a and b
e. one single band corresponding to band b
f. two bands corresponding to b and c
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