Topic 2.3.1 - Cell cycle and chromosomes Flashcards
What are the 2 main parts of the cell cycle?
Mitosis and interphase
What happens in the G1 phase?
Cell replicates organelles
This requires a lot of protein so transcription and translation occur
Size of cell increases so that daughter cells will be correct size
What happens in the S phase?
DNA content doubles
New chromatids form
Number of chromosomes stay the same however
so the cell needs to synthesise a lot of DNA
What happens during the G2 phase?
The cell replaces energy stores used during the s phase.
Continuation of transcription and translation
If any chromosomes are damaged they’re repaired
Cell growth
What are the two stages in the mitotic phase?
Mitosis
Cytokinesis
What is the G0 phase
When a cell exits the cell cycle
Reasons why cells enter the G0 phase.
Fully differentiated cells enter forever e.g adult nerve cells
DNA in cells can become damaged and then the cell will no longer be able to divide - senescent cells
B memory cells enter temporarily but can be triggered to re-enter cell cycle during infection
What happens if a cell fails at a checkpoint?
It leaves the cell cycle and enters G0
What are the 3 checkpoints in the cell cycle?
G1 checkpoint
G2 checkpoint
Metaphase checkpoint
What happens at the G1 checkpoint?
Cell is checked if it’s the correct size before entering the s phase
Also looks for DNA damage
What happens at the G2 checkpoint?
Again checked for DNA damage
And checks that the cell has grown to the correct size
What happens at the metaphase checkpoint?
Checks chromosomes are assembled correctly on the mitotic spindle
Once passed, the cell can enter cytokinesis
How is DNA packed into chromosomes?
DNA wraps around histone proteins, this forms nucleosomes.
Nucleosomes coil and stack together to form fibres called chromatin
Chromatin loops and folds with the help of other proteins to form chromosomes
What’s a karyotype?
An individuals collection of chromosomes
