Module 2.6 - Cell Division, Cell Diversity And Cell Differentiation

Question 1

Define the cell cycle

Answer 1

The cell cycle describes the events that take place as one parent cell divides to produce 2 new daughter cells which then each grow to full size

Question 2

Gap 1

Answer 2

Cells grow and increase in size
Biosynthesis (protein synthesis, make enzymes needed for DNA replication in S phase)
Organelles duplicate

Question 3

Gap 2

Answer 3

Chemicals ensure the cell is ready for mitosis by stimulating proteins that will be involved in making chromosomes condense and in formation of the spindle
Cells grow

Question 4

Gap 0

Answer 4

Resting phase triggered during early G1 at restriction point by a checkpoint chemical
Some cells (e.g. epithelial cells lining the gut) don’t have this phase or remain in it indefinitely (e.g. neurones)
Cells may undergo apoptosis, differentiation or senescence

Question 5

Synthesis

Answer 5

DNA replicates
Chromosomes duplicate to consist of a pair of identical sister chromatids
Rapid phase as the exposed DNA base pairs are more susceptible to mutagenic agents

Question 6

Main checkpoints

Answer 6

G1/S checkpoint or restriction point

G2/M checkpoint

Question 7

Purpose of checkpoints

Answer 7

Prevent uncontrollable division that would lead to tumours
Detect and repair damage to DNA
Ensure cycle cannot be reversed
Ensure DNA is only duplicated once during each cycle