2. Cell Cycle & Mitosis Flashcards
3 phases of the cell cycle
- Interphase
- Mitosis
- Cytokinesis
In a nutshell, what happens in interphase?
Cell prepares for mitosis whilst also carrying out its normal cell functions
In a nutshell, what happens in mitosis?
Division of the nucleus (aka. nuclear division)
In a nutshell, what happens in cytokinesis?
Division of the cytoplasm
Which stage of the cell cycle is the longest?
Interphase
Rather than dividing, what does the cell do in interphase?
Normal cell activities e.g. respiration, protein synthesis.
Very metabolically active
What happens in G1?
Organelle synthesis
Cytoplasm increases in volume
What happens in the S phase?
Semi-conservative DNA replication: chromosomes replicated to form chromatids and new histones are synthesised
What happens in G2?
Further synthesis of proteins & organelles.
Preparation for mitosis (replicated DNA checked for errors & corrected if necessary)
Which cells in the human body divide the fastest?
Hair follicle cells
Skin cells
Bone marrow cells
Which cells in the human body divide the slowest?
Nerve cells - they don’t replicate!
Almost like they are in constant interphase
What is a homologous pair of chromosomes?
Pairs of chromosomes that have the same genes but potentially different alleles
What is chromatin?
DNA when it is not wound up tightly as a chromosome
Purposes of mitosis
Growth
To replace damaged or worn out cells
Two things mitosis is affected by
The environment of the cell
Growth factors
Which two genes regulate mitosis?
Proto-oncogenes
Tumour suppressor genes
In cancer, what is the uncontrolled cell growth and division caused by?
Damage to the genes that control mitosis and the cell cycle
What is metastasis?
The process whereby a tumour in one part of the body spreads via the bloodstream to other parts of the body
What do proto-oncogenes do in terms of controlling the cell cycle?
They speed it up
Like the fuel/gas of a car
What do tumour suppressor genes do in terms of controlling the cell cycle?
They slow it down
Like the brakes of a car
What is an oncogene?
A mutated proto-oncogene working too much or too fast
What are the main treatments for cancer?
Surgery (to remove the tumour)
Radiotherapy - radiation damages the DNA of cells in the tumour
Chemotherapy
What are some examples of chemotherapy?
Blocking enzymes involved in DNA replication
Preventing DNA unwinding
Inhibiting synthesis of new nucleotides
Preventing development of the spindle
Side effects of chemotherapy include…
Hair loss
Severe nausea: cells in digestive system divide rapidly
What is immunotherapy?
Another newer type of cancer treatment
Essentially getting the immune system to recognise abnormal cells & kill them
What does mitosis produce?
Genetically identical daughter cells
What are the 3 processes in living things that require mitosis?
Growth
Repair
Asexual reproduction
Stages of mitosis in order
Prophase Metaphase Anaphase Telophase (PMAT)
Prophase
- Chromosomes condense/supercoil
- Centrioles migrate to opposite ends/poles of the cell
- Microtubules start to develop from each centriole with some spanning the cell from pole to pole - these are spindle fibres
- Nuclear membrane breaks down
Metaphase
Chromosomes line up at the equator & attach to certain spindle fibres at their centromeres
Anaphase
The chromosomes (sister chromatids) split apart at the centromere as they are pulled to opposite poles of the cell by the spindle fibres
Telophase
Spindle fibres break down & a new nuclear envelope forms around each group of chromsomes
Cytokinesis
The cell constricts inwards from its middle until the cell physically splits into two separate cells
Why is telophase/cytokinesis in plant cells different from animal cells?
There is a cell wall!
What happens in telophase of plant cells?
Vesicles filled with cell wall components separate the two halves of the cell and fuse to form a growing cell plate (see Onenote)
