Regulation of Cell Growth & Death

Question 1

A cell has a high cyclin B-dependent kinase activity. What does this tell you?
A. The cell is in G0
B. The cell is in the G1 phase
C. The cell in the G2 phase
D. The cell is in mitosis
E. The cell is in S phase

Answer 1

D. The cell is in mitosis

cyclyin D = R point

Question 2

Dynamic equilibrium of microtubules refers to
A. the balance between rescue and catastrophe of microtubules
B. the balance of forces in the mitotic spindle
C. the oscillation of cell volume around an equilibrium point
D. the regulation of expression of tubulin genes
E. the regulation of glycosylation of tubulin proteins

Answer 2

A. the balance between rescue and catastrophe of microtubules

This alternating behavior of growth and shrinkage is called dynamic equilibrium.
Microtubules are in dynamic equilibrium at the +end, with alternating catastrophe and rescue events.

Question 3

Cells prepare for DNA synthesis during the phase of the cell cycle called:
A. G1
B. G2
C. M
D. T
E. S

Answer 3

A. G1

Question 4

The major role of the polar microtubules is to:
A. assist in the duplication of centrosomes
B. decrease the distance between the migrating chromatids and the centrosomes
C. enhance the poleward slide of the opposing centrosomes during telophase
D. orient the mitotic sppindle with respect to the direction of eventual cell division
E. promote nuclear envelope reassembly after telophase

Answer 4

C. enhance the poleward slide of the opposing centrosomes during telophase

During the latter part of anaphase (Anaphase B), the polar microtubules elongate but at the same time begin a poleward sliding movement relative to the microtubules from the opposite pole that they overlap with. This mechanism pushes the centrosomes apart. The poleward slide of the overlapping polar microtubules is mediated by motor proteins at the +ends of the polar microtubules. As a result, the entire mitotic spindle becomes elongated and thinned. At the same time, –end shortening of astral microtubules which are attached to the cell cortices results in the centrosomes being pulled further apart.

Question 5

A chromsome has two centromeres (dicentric). Which is true?
A. An isochromosome will form in the next cell division
B. A ring chromosome will form in the next cell divison
C. One of the two centromeres will be functionally suppressed because each chromosome can only “tolerate” one centromere
D. The cell will die in the next cell divison becuase the chromosome will break into mulitple fragments.
E. The dicentric chromosome will be entirely deleted from the genome.

Answer 5

C. One of the two centromeres will be functionally suppressed because each chromosome can only “tolerate” one centromere

Question 6

In mitotic telophase, sister chromatids separate and migrate away from each other towards its own centrosome. During this stage, the chromosomes assume a shape like a C (or its mirror image), with the convex end pointing towards the centrosome it is migrating towards. This is explained mostly by

an ejection or pulling force of the kinetochoric microtbues & an ejection of pulling force of the polar microtubules

Answer 6

a pulling force of the kinetochore microtubules and an ejection force of the polar microtubules

Question 7

Which one of the following descriptions about the telomere is correct?
A. It consists of alpha-satellite DNA
B. It consists of condensins and cohesins
C. It interacts with polar microtubules to help maintain the integrity of the mitotic spindle
D. It is responsible for the initiation of DNA replication
E. It is absent from the p arm of acrocentric chromosomes

Answer 7

C. It interacts with polar microtubules to help maintain the integrity of the mitotic spindle

Question 8

Which one of the following structures is the attachment ponit for kinetochore microtubules during cell division?
A. Centromere
B. Nucleosome
C. Origins of replication
D. Satellite
E. Telomere

Answer 8

A. Centromere

Question 9

What is the equation for: How many different genotypes can you expect in the population with respect to the locus?

Answer 9

n = n(n+1) / 2

Question 10

Nerve growth factor is currently being tested in clinical trials as a therpay for Alzheimer’s disease. One of the effects of nerve growth factor on cells in the brain is to increase the xpression of survival promoting Bcl-2 family proteins. This is believe to decrease the vulnerability of brain cells to toxic stimuli by:
A. inhibiting the bidning of FaS ligand to the death receptor Fas
B. Inhibiting the degredation of APAF-1
C. Inhibiting the release of cytochrome c from mitochondria
D. preventing cells from prematurely entering the cell cycle
E. preventing cells from undergoing necrosis

Answer 10

C. Inhibiting the release of cytochrome c from mitochondria

Question 11

A chromosomal translocation involving the Bcl-2 gene can give rise to a type of cancer called B-cell lymphoma. Given your understanding of Bcl-2 funtion, which one of the following best describes the consequence of this mutation involving Bcl-2?
A. The mutation results in decreased expression of Bcl-2
B. The mutation results in decreased phosphorylation of Bcl02
C. The mutation results in increased expression of Bcl-2
D. The mutation results in increased phosphorylation of Bcl-2
E. The mutation reults in loss of the dimerization domain in Bcl-2

Answer 11

C. The mutation results in increased expression of Bcl-2

bcl-2 is anti-apoptotic

Cancer cells adapt to hypoxic microenvironment by changing to a more aggressive phenotype. This appears to be mediated by the “natural” selection for cells that have undergone a tumor suppressor gene mutation (e.g. TP53) or
have increased expression of an anti-apoptotic gene (e.g. bcl-2). The net effect is decreased tumor cell apoptosis

Question 12

What are caspases?

Answer 12

Caspases are a family of protease enzymes playing essential roles in programmed cell death. They are named caspases due to their specific cysteine protease activity – a cysteine in its active site nucleophilically attacks and cleaves a target protein only after an aspartic acid residue.

Question 13

1. DNA damange from sunburn
2. keratinocytes in basal layer of epidermis half cell cycle progression

How does this happen?

A. cyclin-D dependent kinase complexes are destroyed
B. dermis stops producgin mitogenic signals
C. E2F transcription factor synthesis is truend off
D. induction of the cell cycle inhibitor p21 blocks cyclin-dependent kinases
E. Rb phosphatase activity is increased

Answer 13

D. induction of the cell cycle inhibitor p21 blocks cyclin-dependent kinases

Question 14

Retinoblastoma protein functions as a tumor sppressor becuase it
A. binds to E2F, therby inhibiting transcription of genes necessary for S-phase
B. binds to G1 cyclins, therby preventing cyclin-dependent kinase activation
C. phosphorylates and activates cyclin-dependent kinases
D. promotes cell cycle arrest in response to DNA damange
E. ubiquitinates and degrades cycling-dependent kinase inhibitors

Answer 14

A. binds to E2F, therby inhibiting transcription of genes necessary for S-phase

Question 15

The Rb tumor suppressor protein regulates transition from G1 into S-phase of the celll cycle. What is the mechanistic basis of this control?
A. Phorphorylation of Rb by cyclin-dependent kinases releases bound E2F transcription factors
B. Phosphorylation of Rb by cyclin-dependent kinases releases Rb from the nucleus to the cytoplasm
C. Rb phosphatase activates Rb and increases its affinity for E2F transcription factors

Answer 15

A. Phorphorylation of Rb by cyclin-dependent kinases releases bound E2F transcription factors

Question 16

Progression of the cell cycle through G1, S, and M-phase is driven by complexes made up of
A. distint cyclins and cyclin-dependent kinase inhibitors
B. distant cyclins and cyclin-dependent kinases
C. distinct cyclins, pRb, and E2F
D. gatekeepers and caretakers such as pRb and p53
E. RAS, MYC, and E2F

Answer 16

B. distant cyclins and cyclin-dependent kinases

Question 17

Recessive loss of function mutations that contribute to development of cancer are in what type of genes?

Answer 17

tumor suppressor genes

Question 18

Which one of the following describes the actions of a drug that inhibits the Akt enzyme?
A. it should increase sserine/threonine phosphorylation and increase cell death
B. It shouldl increase tyrosine phosphorylation and reduce cell death.
C. It should reduce serine/threonine phosphorylation and increase cell death

Answer 18

C. It should reduce serine/threonine phosphorylation and increase cell death

Question 19

Inflammation is generally absent during apoptosis in tissues becuase apoptotic cells
A. are degraded by extracellular proteases, lipases, and endonucleases
B. are engulfed by phagocytic cells while their plasma membrances are stil intact
C. contain autolysins that degrade the cell and its membrances

Answer 19

B. are engulfed by phagocytic cells while their plasma membrances are stil intact

Question 20

A gain of funtion mutation in Bcl-2 could result in

Answer 20

decreased cell death

Question 21

A hallmark of B-cell follicular lymphoma is a chromosomal translocation, t(14;18), that results in the long term survival of B-cells normally destined to undergo apoptosis. The direct consequence of the translocation is increased expression of a protein that regulates cell death by preventing release of cytochrome c from mitochondria. The gene affected by the translocation is
A. AFAF-1
B. Bax
C. Bcl-2
D. BCR-ABL
E. Fas

Answer 21

C. Bcl-2

Burkitt Lymphome is a B cell lymphoma also but is t(8;14)
BCR-ABL is the Philadelphia chromsome and is t(9;22) and leads to CML