2.1.6 - cell division, cell and organisation Flashcards
what are the 4 stages of the cell cycle
G1, S, G2 and M (mitosis)
what happens in G1
the cell grows and inc size
transcription of DNA to mRNA
organelles duplicate
biosynthesis happens
what is biosynthesis
where the enzymes needed for the other stages are made
what gene controls G1
p53 (tumour suppressor gene) controls this phase and stops excess growth
what can happen if the p53 gene doesn’t control the cell growth
cell may grow too much and develop into a tumour which could be cancerous
what happens at the early G1 checkpoint
if the cell isn’t progressing properly, it enters G0
what happens at G0
the cell enters to be repaired or sometimes it may have to stay there permanently
what are the reasons that a cell may enter G0 permanently
if it has differentiated into a cell that doesn’t go through mitosis
if the DNA is beyond repair
what happens to a cell in G0 if it is beyond repair
apoptosis (controlled cell death)
senescence (cell ages until death)
what happens at the G1/S checkpoint
if the cell is damaged, it won’t enter the S phase
what happens in the S phase (replication phase)
the DNA duplicates
why is the S phase rapid
to reduce the chance of mutations
what is the order of the genes that are duplicated in the S phase
- housekeeping genes (genes switched on in all cell types)
- genes active in that cell type
- genes normally switched off in that cell type
what happens at the DNA synthesis checkpoint
checks that DNA is replicated properly before entering G2
what happens in G2
additional growth
energy stores replenished
cytoskeleton dismantled
organelles arranged in the cytoplasm
