Cell Cycle & Mitosis, Cell Death

Question 1

When would a cell need to pause in performing its functions?

Answer 1

when it is going through cell division (mitosis)

Question 2

What is a static cell population? Give an example.

Answer 2

Cells that no longer undergo the cell cycle and cell division post natally
Example: neurons

Question 3

Stable cell population vs renewing cell populations

Answer 3

Stable: cells can undergo the cell cycle if induced to do so (regulated; not constant)

Renewing: cells that show a constant level of cell division (although rate can vary in different tissues/organ systems

Question 4

The two broad groups of the cell cycle

Answer 4

Interphase and mitosis

Question 5

What happens during S phase?

Answer 5

DNA is replicated (and condensed into pairs of chromosomes)

Question 6

What happens in each phase of mitosis?

Answer 6

Prophase: centrioles form microtubules; rupture of nuclear envelope
Metaphase: chromosomes line up in the middle; nuclear envelope and nucleolus disappear
Anaphase: each set of chromosomes migrate to opposite ends
Telophase: cell divides into two cells

Question 7

5 step process of how centrioles form the mitotic spindle

Answer 7

1. Two centrioles locate themselves near the nucleus
2. Centrioles form MTOC (microtubule organizing center)
3. Microtubules are assembled and grow outward from centriole
4. During mitosis, the two centrioles that form the spindle will move to opposite sides of the cell, thus lengthening the microtubules they form.
5. Nuclear envelope dissolves and allows chromosomes to attach to the microtubules of the mitotic spindle

Question 8

If damage is detected at G1 damage checkpoint, levels of ___ increase which does what?

Answer 8

Levels of p53 increase which inhibits entry into S phase and can activate programmed cell death

Question 9

G1 restriction checkpoint, if needed, will activate two proteins: __ and __.
What do these proteins do?

Answer 9

E2F and pRb
If a stem cell should differentiate into a mature specialized type of cell rather than dividing, these proteins will prevent S phase and favor exit of the cell cycle into G0.

Question 10

G2 phase has two checkpoints. What do each do?

Answer 10

G2 unreplicated checkpoint monitors completeness of DNA. Any non-replicated DNA will suppress entry to M phase

G2 damage checkpoint: detected damage will lead to arrest of the cell cycle

Question 11

What are cyclins? What is their general function?

Answer 11

They are proteins that push things forward by promoting expression of proteins involved in DNA replication

Question 12

Function of tumor suppressor genes?

Give an example of one.

Answer 12

Prevent entry into the cell cycle

P53

Question 13

What is necrosis and what does it represent?

Answer 13

Cell becomes structurally damaged or experiences a severe disruption of vital functions that leads to rupture of the cell. Necrosis represents a cell’s loss of control over it’s own function

Question 14

What is apoptosis?

Answer 14

Premeditated cell death (doesn’t come from loss of control)

Question 15

Two broad categories of activating apoptosis

Answer 15

1. Intracellular mechanisms: if there is DNA damage, failure of cells to properly mature, etc.
2. Normal or abnormal conditions: During development, some unnecessary or excess cells will be eliminated and replaced by new mature cells; activated during disease process to prevent necrosis and collateral damage

Question 16

In order to suppress apoptosis, there must be a balance between two proteins:

Answer 16

Cell survival promoting proteins (Bcl-2) and pro-apoptotic proteins

Question 17

What can happen as a result of an absence of centrioles or an abnormal spindle?

Answer 17

Alignment would be off which can result in an abnormal number of chromosomes.