Prok & Euk Part 3: Cancer Flashcards
What are the causative factors of cancer?
- Heredity causes
- Chemical carcinogens
- Ionising radiation
- Loss of immunity
What are proto-oncogenes?
Proto-oncogenes are normal cellular genes which codes for proteins that are involved in regulation of normal cell division
What are proto-oncogenes called when they mutate?
Oncogenes
What are the products of proto-oncogenes?
- Proteins derived from proto-oncogenes
- Involved in stimulating normal cell division
How do proto-oncogenes turn into oncogenes?
gain-in-function mutation
What are tumour suppressor genes?
It is normal cellular genes that code for products that inhibit cell division and helps to prevent uncontrolled cell division, they can activate cell cycle arrest, DNA repair or apoptosis.
When do tumour suppresor genes contribute to cancer?
When there is a loss-of-function mutation
What are the 2 types of tumour?
Benign and Malignant
What is a benign tumour?
It is localised tumour that does not spread to other regions
What is a malignant tumour?
It is a benign tumour that turned cancerous due to accumulation of mutation from continual cell divisions. It is invasive and has the ability to undergo metastasis (spread to other parts of the body).
Example of a proto-oncogene?
ras gene
What does the ras gene code for?
It codes for Ras proteins involved in signal transduction pathways
How does Ras protein gets activated?
Binding of a growth factor to the receptor triggers a series of reaction which includes the binding of GTP to an inactive Ras protein, activating the Ras protein
What is the function of the Ras protein?
Activated Ras proteins transduce signals from the growth factor to signalling processes, thereby leading to cell division.
What is the result of a mutation in ras gene?
It results in a constitutively active Ras protein, leading to increased cell division even when growth factor not binded to receptor
What does the p53 gene code for?
It code for specific transcription factors, p53 protein.
What does p53 protein do?
It binds to DNA to promote synthesis of cell cycle-inhibiting proteins, therefore p53 protein functions as an activator
What is the normal role of p53 protein?
It upregulates expression of genes involved in:
- cell cycle arrest
- DNA repair
- (if DNA beyond repair) initiates apoptosis (cell death)
What is the result of a mutation in p53 gene?
Defective p53 protein will not restrict cell proliferation, instead, cell cycle continues without repairing DNA/cell does not undergo apoptosis, thus allowing mutations to accumulate.
What are the number of alleles needed to be mutated for gain-in-function mutation to be cancerous?
Only one copy of allele needs to be mutated, known as dominant mutation
What are the number of alleles needed to mutated for loss-in-function mutation to be cancerous?
Both copies of alleles need to be mutated, known as recessive mutation
