the cell cycle

Question 1

What is the purpose of checkpoints?

Answer 1

-to prevent uncontrollable cell division that would lead to tumours
-to detect and repair damage to DNA (e.g. caused by UV light)

Because molecular events that control the cell cycle happens in a specific sequence, it ensure that:
-cycle cannot be reversed
-DNA is only duplicated once

Question 2

What happens in the M phase?

Answer 2

-checks for chromosome attachment to spindle
-cell growth stops
-nuclear division (prophase, metaphase, anaphase and telophase)
-cytokinesis

Question 3

What happens in the G1 phase?

Answer 3

-checks for cell size, nutrients, growth factors, DNA damage
-transcription of genes to make RNA
-organelles duplicate
-protein synthesis e.g. making enzymes needed for S phase

Question 4

What happens in the G0 phase?

Answer 4

resting state

may undergo:
-apoptosis (programmed cell death)
-differentiation
-senescence (can no longer divide)

Question 5

What happens in the S phase?

Answer 5

-DNA synthesis
-DNA replicates- when all chromosomes duplicate, each one consists of a pair of identical sister chromatids
-rapid phase

Question 6

What happens in the G2 phase?

Answer 6

checks for cell size, DNA replication and damage
special chemicals ensures cell is ready for mitosis by stimulating proteins involved in making chromosomes condense in formation of the spindle
cell grows