Cell division Flashcards
What is contact inhibition of growth and how is it relevant to cancer?
Cells normally stop growing by sensing neighbouring cells
Tumours usually lack contact inhibition so don’t stop growing
What do cells have to do before they can divide?
Duplicate their genetic material
What is the most vulnerable part of the cell cycle?
Mitosis- happens quickly to avoid risk
What phase is a normal resting cell in?
G0
Where do cells enter the cell cycle?
Gap phase 1 (G1)
What follows G1 and what happens in that phase?
Synthesis (S) phase where duplication takes place
What happens once duplication has taken place?
It enters G2 (decision point) where the cell checks that everything is ok and ready to go into mitosis
What occurs in the S phase?
DNA replication
Protein synthesis: initiation of translation and elongation increased; capacity is also increased
Replication of organelles (centrosomes, mitochondria, Golgi etc)
What is a centrosome?
An organelle near the nucleus of a cell which contains the 2 centrioles and from which the spindle fibres develop in cell division
What are the two centrioles referred to as and what do they do?
The mother and daughter centrioles- they regulate the microtubule network to orchestrate cell division
What are centrioles made of?
Microtubules
What happens to the centrioles in the G1 phase?
Separation of mother and daughter centrioles
What happens once the centrioles separate?
They start to duplicate in the S phase- the mother centriole will produce a daughter and the daughter will produce a mother
What is there surrounding the centrioles?
Cloud of protein complexes- there are points where they make nucleating sites for the microtubules
What is nucleation?
When you put microtubules together
What happens at nucleating sites as the cell encounters a need for mitosis?
Microtubules start to grow from these points and form an array of microtubules
What are the 6 phases of mitosis?
Interphase Prophase Metaphase Anaphase Telophase Cytokinesis
What happens during prophase?
Condensation of duplicated DNA
Why does the duplicated DNA need to be condensed?
Minimise DNA damage during mitosis
How is the DNA condensed in prophase?
Double helices are wrapped around histones to form beads on a string form of a chromatin which compacts the chromatin from being 2nm wide to 11nm wide
The string is then further wrapped around itself to form 30nm fibres, these fibres are then extended as a scaffold forming a chromosome scaffold- compacting it to 300nm wide, it is then further wrapped until you end up with a chromosome
What is a centromere?
Constriction around the chromosomes (like a belt)