Cell Division

Question 1

Name 3 different asexual reproduction methods in which cell division is involved.

Answer 1

• Binary Fission
• Budding
• Parthenogenesis

Question 2

Name all phases of the cell cycle

Answer 2

G1 phase- Cells double in size
S phase- DNA replication occurs
G2 phase- Organelles are duplicated and cell prepares for mitosis
Prophase- Chromatin condense and become visible. Nuclear envelope breaks down.
Metaphase- Chromosomes visible and arrange at central plane of cell (metaphase plate)
Anaphase- Sister chromatids are pulled to opposite poles of cell. Now two single chromatid chromosomes
Telophase- new nuclei reform, chromatin decondenses and the interphase cytoskeleton is established

Question 3

What happens during cytokinesis?

Answer 3

A cleavage furrow forms between the two nuclei on the original plane of the metaphase plate. Pinching off to form two separate cells.

Question 4

How is the cell cycle controlled?

Answer 4

• Checkpoints through the cell cycle.

- Only very few cells retain the ability to divide

Question 5

What would happen if DNA was damaged during the G1 stage?

Answer 5

• This would activate the G1/S-phase checkpoint, arresting the cell cycle.
• Time is allowed for repairs to DNA before replication
• If repair is not possible then the cell will initiate apoptosis

Question 6

How is the G1 checkpoint controlled?

Answer 6

A retinoblastoma protein actively blocks the cell cycle. This is inactivated by a CDK (cyclin dependant kinase) the CDK can only inactivate it if it forms a complex with cyclin. This will only be produced if DNA replication occurs with no errors.