Biology 2100 Exam 3 UPDATED ACTUAL Questions and CORRECT Answers

Biology 2100 Exam 3
UPDATED ACTUAL Questions and CORRECT Answers

Question: What is cyclin?

Correct Answer: Cyclin is a protein that is directly involved in the regulation of part the cell cycle.

Question: What role does cyclin play in the cell cycle?

Correct Answer: Cyclin is a protein that ac- tivates CDKs in order to trigger certain processes that

signal the passing of a checkpoint.

Question: What parts of the cell cycle does cyclin/CDK affect?

Correct Answer: MPF (Cyclin and CDK to- gether) is responsible for a cell's transition into Mito- sis

from the G2 phase; G1 to S phase; and passing of the metaphase check- point.

Question: What is CDK and what does it do?

Correct Answer: CDK is a kinase that uses Cyclin as a substrate to phosphorylate other mol- ecules in

the cell in order to pass the G2 checkpoint of the cell cycle

Question: What is MPF and what process(es) does it promote?

Correct Answer: MPF describes CDK and Cyclin together as a com- plex. Together, they pro- mote

processes that trig- ger the transition from G2 phase to M-phase. These are directly

related to the G2 checkpoint.

Question: How do cell cycle checkpoints differ from CDK/cyclin complexes? How are they related?

Correct Answer: G1 and G2 and S check- points use CDK complex- es for different functions in order

to pass the relative checkpoints.

Question: p53 is a molecule (protein) that enters cells and is nat- urally targeted, exported, and

destroyed when no damage to DNA has oc- curred internally.

Correct Answer: What is p53?

, Question: What does p53 do and why is it important?

Correct Answer: When p53 encounters DNA damage within a cell, it is phosphorylated and afterwards

cannot be targeted as normal. This causes a buildup of p53 in the cell, which can

subse- quently cause the cell cycle to pause until the damage is repaired, or it can

lead to apoptosis.

Question: Create an example illustrating the role of p53 in the human body.

Correct Answer: Inside a human liver cell, DNA damage oc- curred during the synthe- sis phase. p53

enters the molecule during the G2 to M phase checkpoint and correctly detects the

DNA damage, and is phospho- rylated. p53 accumulates and pauses the cell cy- cle.

After some time it trig- gers apoptosis and the cell dies.

Question: What might one expect to occur if a person's p53 fails to function properly?

Correct Answer: If p53 fails to properly de- tect DNA damage, or for whatever reason it cannot be

phosphorylated when detecting damage, the de- funct/damaged cell will pass the cell

cycle check- points and can potentially pass on any DNA damage to its daughter

cells. This will continue down the line of cell production if the subsequent p53 mole-

cules of the daughter cells also fail--potentially lead- ing to disastrous amounts of

improper/malfunction- ing cells.

Question: List the three cell cycle checkpoints, and their place in the cell cycle (what comes before and

after them).

Correct Answer: 1) G1 to S checkpoint (Mi- tosis has just occurred, cell is determining if it will

divide; if the checkpoint does not pass, it will enter G0 or die). 2) G2 to Mi- tosis

Checkpoint (The cell has replicated DNA in S phase and is preparing to enter mitosis;

p53 will search for DNA damage, and cell size must be ap- propriate to enter

mitosis.) 3) M-phase (metaphase) checkpoint (the cell has condensed its chromo-

somes and it is ensuring that spindle assembly is correct-- all chromosomes must be

lined up in the middle of the cell, all must be attached to spindles before anaphase

can oc- cur after.