What are the stages of the cell cycle?
Interphase (G1, S phase and G2)
Mitosis (Prophase, metaphase, anaphase and telophase)
Cytokinesis
What happens during interphase?
G1 - Cell grows in size and produces RNA, proteins and enzymes. And receives a signal to divide
S phase - The DNA is replicated in the nucleus (semi-conservatively)
G2 - Cell continues to grow and the newly synthesised DNA is checked.
What is the order of mitosis?
1) Prophase
2) Metaphase
3) Anaphase
4) Telophase (Cytokinesis)
What happens in prophase?
Chromosomes condense and become visible.
Nuclear envelope disintegrates
Nucleolus disappears
Spindle fibres begin to develop
What happens in metaphase?
The chromosomes line up at the equator of the cell.
Spindle fibres attach themselves to the centromere of each chromosome.
What happens in anaphase?
The spindle fibres contract and pull the sister chromatids to opposite poles of the cell.
What happens in telophase?
Chromosomes begin to unravel and condense.
Spindle fibres disintegrate.
Nuclear envelope reforms.
What happens in cytokinesis?
The cytoplasm and cell membrane divide.
Two genetically identical daughter cells are formed.
What is mitosis?
Part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells,each with the identical copies of DNA produced by the parent cell during DNA replication.
What can uncontrolled division of cells lead to?
Tumours and/ of cancer
Why do most cancer treatments target the rate of cell division?
As cancer cells are rapidly dividing so have a short interphase to quickly re-enter mitosis. Many cancer treatments target mitosis and a specific function happening (e.g chromatid separation)
Therefore if the drugs prevents mitosis then the cancer cell can no longer replicate preventing tumour growth.
Why do you lose hair and have a weakened immune system undergoing cancer treatments?
As hair follicles and bone marrow have a higher proportion of cells in mitosis so they get affected more than the normal healthy cells with a longer interphase and less proportion in mitosis.
Why do you have numerous rounds of cancer treatment?
-To give the healthy cells time to recover (less amount of healthy cells in mitosis so less are affected)
-Cant be continuous as too many cells would be harmed.
Describe Binary fission (of prokaryotic cells)?
1) Circular DNA and plasmids are replicated (and attach to the cell membrane).
2) The cytoplasm and cell membrane divide into two.
3) Each daughter cell receives a single copy of circular DNA and a variable number of plasmids (depending of if there is any)
Why don’t viruses undergo DNA replication?
They are acellular
How do viruses multiply?
1) Virus will inject their nucleic acid (DNA/RNA) into a host cell by using the attachment proteins on its surface to bind to complementary receptors on the host cell.
2) Host cell uses the viruses nucleic acid and ribosomes to produce new viral particles.
3) The new viral particles are released via the cell surface membrane and often take a piece of the membrane with them, destroying the host cell.
