2.6- Cell Divison, Cell Cycle And Cell Differentiation

Question 1

What is the definition of interphase?

Answer 1

The phase of the cell cycle where the cell is not dividing, it is subdivided into growth and synthesis phases

Question 2

What is mitosis?

Answer 2

A type of nuclear division that produces daughter cells that are genetically identical to eachother and to the parent cell

Question 3

What is cytokinesis?

Answer 3

Cytoplasmic division following nuclear division, resulting in two new daughter cells

Question 4

What is nuclear and cytoplasmic division referred to as?

Answer 4

The M phase

Question 5

What are the two main checkpoints in the regulation of the eukaryotic cell cycle?

Answer 5

G1/S- also called the restriction point
and the G2/M checkpoint
Their purposes are to:
- prevent uncontrolled cell division
- to detect and repair damage to DNA (e.g caused by UV light)
As the molecular events that control the cell cycle happen in a specific sequence, they also ensure that
- the cycle cannot be reversed
- the DNA is only duplicated once during each cycle

Question 6

What is the significance of the P53 gene

Answer 6

Triggers the two main checkpoints in the regulation of the cell cycle
Known as the tumour suppressor gene

Question 7

What occurs in the M phase of the cell cycle

Answer 7

A checkpoint triggers the condensation of chromatin
Halfway through the cycle the G2/M checkpoint ensures that the cell is ready to complete mitosis

• cell growth stops
• mitosis occurs (prophase metaphase anaphase telophase)
• cytokinesis occurs

Question 8

What occurs in the G0 phase

Answer 8

A rest phase triggered during early G1 at the G1/S point by a checkpoint chemical
Some cells eg epithelial cells etc do not have this phase
- cells undergo apoptosis , differentiation or senescence
- some types of cells e.g neurones remain in this phase for a very long time/ indefinitely