20.5 Gene expression and cancer Flashcards
How does the appearance of the nucleus differ between benign and malignant tumours
In benign it appears normal
In malignant it is a lot darker because it contains lots of DNA
Do benign or malignant tumours produce adhesion molecules
Which is metastasis
Benign produce adhesion molecules to stick them together so they remain in the tissue from which they arise
Malignant molecules do not produce adhesion molecules so they spread to other parts of the body in a process called metastasis
Do benign or malignant tumours have a capsule
Benign have a capsule of dense tissue so remain compact structure
Malignant don’t contain a capsule so can grow into surrounding tissue
Where do cancer cells derive from
A single mutated cell can cause uncontrolled mitosis
What are proto-oncogenes
Proto-oncogenes stimulate a cell to divide when growth factors attach to promotor region on its cell membrane
This can activate the genes that cause DNA to replicate so the cell divides
what are oncogenes
Oncogenes are mutations of proto-oncogenes, and it can become permanently activated.
This means the DNA will keep replicating so cells keep dividing
What two reasons are there for why an oncogene can be permanently activated
- Receptor protein on cell surface membrane can be permanently activated so cell division continues even if there are no growth factors binding to it.
- The oncogene may code for a growth factor which is then produced in excessive amounts so more cell division is induced
What are tumour suppressor genes
- They slow down cell division, repair mistakes in DNA and tell cells when to die (in process called apoptosis)
So opposite role to oncogenes, as they stop formation of tumours
What happens if a tumour suppressor gene is mutated, eg turns off
It stops inhibiting cell division so cells can grow out of control
This means when mutated cells are formed, which are structurally and functionally different to normal cells.
These might not all die so can clone and form tumours
What would hypermethylation of tumour suppressor genes do
- Hypermethylation means too many methyl groups bind to promoter region
- So this can cause DNA to coil up to hide the gene so the tumour suppressor gene is inactivated
- Transcription of promotor regions of DNA is inhibited
As tumour suppressor genes roll is to slow down cell division, this means tumours are more likely to form as cells divide more
What would hypomethylation of oncogenes do
- Not enough methyl groups bind to promotor region of DNA
- So their gene is activated and transcription can occur to permanently switch the gene on
Why does risk of womens breast cancer increase after menopause
Oestrogen starts being produced in fat cells in the breasts, so higher concentration there.
A tumour can develop which will also produce oestrogen and so grow tumours more
Why does oestrogen cause tumour to develop
Oestrogen can bind to gene to start transcription
If the gene oestrogen binds to is one that controls cell division and growth, it is activated and divides more to produce a tumour
Eg oestrogen causes proto-oncogenes to develop into oncogenes
