Mitosis/Cancer Flashcards
Why does only use the first few mm from the root (mitosis practical)?
Where the dividing cells are/ where mitosis occurs
Why do we press down firmly on the cover slip (mitosis practical)?
to produce a single layer of cells to let light through
Why should you not push the coverslip sideways?
to avoid rolling cells together and breaking chromosomes
Describe and explain how to make a mitotic index accurate
decide whether you are including only whole cells or other etc = to standardise the counting
examine large number of fields of view = to ensure representative sample
repeat count = to ensure figures are correct
When looking at a cell through a microscope, how do you know that it is going through mitosis (give an explanation to each reason)?
chromosomes are visible = condensed
chromosomes are made up of two chromatids = DNA has replicated
chromosomes are not arranged n homologous pairs = would be if it were meiosis
What is a homologous pair of chromosomes?
two chromosomes that carry the same genes
What is cancer?
Cancer is a group of diseases caused by damage to the genes that regulate mitosis and the cell cycle.
Unrestrained growth of cells occurs and a group of abnormal cells, called a tumour, develops and constantly expands in size.
Which two genes are the cell cycle controlled by and what are their roles?
Proto-oncogenes stimulate division and inhibit cell death
Tumour suppressor genes try to prevent division and encourage cell death!
What happens when a proto-oncogene mutates?
If a proto-oncogene mutates we call it an oncogene.
These cannot be controlled by the tumour suppressor genes and so the cell continues to be stimulated to keep on dividing.
This uncontrolled cell division results in a tumour
What are benign and malignant tumours?
BENIGN = do not spread from their site of origin – they may nevertheless compress and damage adjacent tissues. They are less likely to be life threatening.
Malignant, cancerous tumours grow rapidly and may spread from their site of origin. They are more likely to be life threatening.
Why are malignant tumours more likely to be life-threatening?
These tumours develop their own blood and lymph supply which can transport malignant cells from the tumour to other sites in the body
What is it called when cancerous cells move from their site of origin to a secondary site?
metastasis
Describe how cancer cells metastasise
malignant cells develop,
tumour secretes chemicals,
chemicals stimulate the blood vessels to grow, so they grow around the tumour,
cancer cells detach from the tumour and are transported in the blood.
these cells can also travel through the lymphatic system
A malignant cell squeezes through the blood capillary wall.
Cells start to divide = secondary tumour starts to grow
Describe in detail how cancer forms
How are all cells in an organism produced?
They are produced by mitotic divisions from the fertilised egg = they all contain the same genes
How do stem cells become specialized?
Different genes are expressed and “turned off”
What are epithelial tissues?
- found in aminals
- consists of sheets of cells
- line the surface of organs and often have a protective or secretory function
What are xylem tissues?
- found in plants
- made up of a number of similar cell types
- used to transport water and mineral ions throughout the plant and also gives mechanical support
compare the difference in the ARRANGEMENT of prokaryotic DNA from human DNA
Prokaryotic:
- circular
- not associated with proteins
- shorter
Explain why the process of DNA replication is described as semi-conservative?
During DNA replication, the old strands of DNA are used as templates to create new complementary strands. This means new molecules of DNA ill always be made up of one original strand and one new stand
Many different substances enter and leave a cell by crossing its cell surface membrane. Describe how substances can cross a cell surface membrane (5 marks) (exam question
- Simple diffusion from high to low concentration/ down the concentration gradient
- Small/ non-polar/ lipid-soluble molecules pass via phospholipids bilayer
- water moves by osmosis from high water potential to low water potential
- active transport involving carrier proteins, and requires ATP (for example co transprot) (2 marks in one)
how can bengin tumours cause damage to the body
- damage the specific organ which they occur
- can cause blockages or obstructions
- damage/exert pressure on other organs
