Answer Each Question, Noting Carefully the Instructions for Each

Bio 169 2003 Exam 2 Name______

Biology 169 -- Exam 2

February 25, 2003

Answer each question, noting carefully the instructions for each.

Repeat: Read the instructions for each question before answering!!!

Be as specificand conciseas possible in each answer,

noting the suggested length limits described for each problem.

Please print name on top of each page! (In case pages get separated.)

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I certify that I have performed my work on this examination in full conformity with the provisions of the Honor Code.

Signature______

1. (3 points)What important property of the cell cycle was shown by fusing cells in G1 orcells in G2 with cells in S phase (1 or 2 sentences)?

2. (3 points)Describe an important difference between the cyclin dependent kinases that control the mammalian and yeast cell cycle (1 sentence).

3. (4 points)S. pombe cdc2 mutants and S. cerevisiae cdc28temperature sensitive mutants arrest at different points in the cell cycle. At what point does each of these mutants arrest? Explain why they arrest at different cell-cycle phases (2 sentences).

4. (3 points)What activity preventsthe re-initiation of origins of replication during S and G2 phase, and at what time during the cell cycle is this activity removed (2 sentences)?

5. (2 points) Human genes that regulate the cell cycle were first isolated by (circle one):

a. Biochemical purification

b. Complementation of yeast mutants

c. Complementation of Xenopus mutants

d. Positional cloning

6. (3 points) Describe the difference between a centromere and a kinetochore, and the role they play together during the cell cycle (2 sentences).

7. (2 points) Circle all of the following true statements about eukaryotic S phase.

1. There is a single origin of replication in the genome.

1. All chromosomes must have at least one origin of replication.

1. Each chromosome is replicated twice during S phase of a mitotic cell cycle.

1. There are multiple origins of replication in the genome.

8. (5 points)Investigators found that cyclin B concentration rises and falls in synchrony with mitotic events and MPF activity. However, correlation is not causality. How did they show that cyclin B was responsible for these cell cycle events (4-5 sentences)?

9. (2 points) Circle any of the following statements that are consistent with the known action of the p21 family of cdk inhibitors (i.e. there could be more than one).

a. over expression arrests mammalian cells in G1 phase

b. prevent the transcription of cdk genes

c. simultaneously bind cyclin and cdk

d. interact only with unbound cdk proteins

10. (2 points) Mitotic cyclin levels in early Xenopus embryos are regulated by (circle the best answer):

a. phosphorylation

b. synthesis and degradation of their mRNAs

c. ubiquitination by APC during mitosis

d. transcription by MPF

11. (2 points) Circle any of the following statements that are consistent with the known action of the S. pombewee1 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

13. (2 points) 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

12. (2 points each)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.

ts mutation of cdc2______

ts mutations of cdc13 ______

ts mutation of cdc25______

a wee1 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______

14. (1 point) Name one stimulus for quiescent (G0) cells to re-enter the cell cycle? ______

Name 3 molecularevents that occur within cells during G1after such stimulation (“passage through the restriction point” is not what I’m looking for)(2 points each).

1) ______

2)______

3)______

15. (2 points each)Assume that a wild type mammalian cell in G0 takes 8 hoursto enter S phase after addition of growth factors, and that the Restriction Point occurs 5 hours before the beginning of S phase. Indicate by writing “YES” or “NO” whether a cell will divide at least once or not in each of the following experimental situations.

Continuous incubation incell culture medium containing serum ______

Incubation in medium containing serum for 6 hours,

followed by incubation in medium lacking serum ______

Incubation in medium containing serum for 3 hours,

followed by incubation in medium lacking serum______

Incubation in medium containing serum for 3 hours,

followed by incubation in medium lacking serum for 30 min,

followed by continuous incubation in medium containing serum ______

16.(2 points) Which causes cyclin D to be over expressed in mantle cell lymphoma (circle one)?

a.gene amplification

b.chromosome translocation

c.point mutation

d.mutation of both alleles to the recessive genotype

17. (1 point) E2F controls the transcription of genes encoding proteins that predominantly act in which phase of the cell cycle? ______

18. (2 points) The components of the mammalian restriction point that when mutated lead to cancer include all of the following except (circle one):

a. cyclin Db. p16c. Rbd. cdc2

19. (2 points each) Name three criteria used to establish that the RB gene had been identified.

1)______

2)______

3)______

20. (3 points) Why did Bob Weinberg think that Ted Dryja’s strategy for cloning the RB gene would fail (2 sentences)?

21. (2 points each) Indicated whether the following situations would tend to promotecell cycle progression,inhibit cell cycle progression, or do nothing (use those words).

A cell with a mutant E2F that cannot bind to DNA______

A cell with a mutant pRB that cannot bind to E2F______

A cell with a mutant p16 protein that cannot bind to cdk4______

A cell with a mutant cdk4 that cannot bind to cyclin D______

Expression of a mutant pRB that cannot be phosphorylated by cyclin D/cdk4 ______

Expression of ahyper-stable cyclin D protein______

A deletion of the RB gene______

A deletion of both the RB gene and the cyclin D gene______

A deletion of both the RB gene and the E2F1 gene______

Overexpression of the p16 gene in an RB mutant cell______

Overexpression of the p16 gene in a normal cell______

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