Cell cycle

Question 1

What are G0, S & G2 collectively called?

Answer 1

The interphase.

Question 2

What happens in G1?

Answer 2

Cells are actively growing & preparing for DNA replication. Cyclin G1 binds to CDK 4 and signals the cell to prepare chromosomes for replication.

Question 3

What happens in G0?

Answer 3

G0 is also known as the quiescent phase. The cell is not actively growing here however it is still metabolically active & carrying out cellular functions. Some cells will stay here temporarily whilst others will remain here permanently.

Question 4

What happens in the S phase?

Answer 4

S-phase promoting factor increases & enters the nucleus to initiate DNA replication. This process occurs at slightly different times in each cell, therefore some cells may be 4n (4 copies of DNA / chromosome) whilst others are still 2n. After replication, 2 sister chromatids are held together in a dyad by centromeres until separated by mitosis.

Question 5

What happens in G2?

Answer 5

Cyclin E levels fall and Cyclin B levels rise. During this phase, centrosomes (& centrioles) duplicate.