Prok & Euk Part 3: Cancer

Question 1

What are the causative factors of cancer?

Answer 1

• Heredity causes
• Chemical carcinogens
• Ionising radiation
• Loss of immunity

Question 2

What are proto-oncogenes?

Answer 2

Proto-oncogenes are normal cellular genes which codes for proteins that are involved in regulation of normal cell division

Question 3

What are proto-oncogenes called when they mutate?

Answer 3

Oncogenes

Question 4

What are the products of proto-oncogenes?

Answer 4

• Proteins derived from proto-oncogenes
• Involved in stimulating normal cell division

Question 5

How do proto-oncogenes turn into oncogenes?

Answer 5

gain-in-function mutation

Question 6

What are tumour suppressor genes?

Answer 6

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.

Question 7

When do tumour suppresor genes contribute to cancer?

Answer 7

When there is a loss-of-function mutation

Question 8

What are the 2 types of tumour?

Answer 8

Benign and Malignant

Question 9

What is a benign tumour?

Answer 9

It is localised tumour that does not spread to other regions

Question 10

What is a malignant tumour?

Answer 10

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).

Question 11

Example of a proto-oncogene?

Answer 11

ras gene

Question 12

What does the ras gene code for?

Answer 12

It codes for Ras proteins involved in signal transduction pathways

Question 13

How does Ras protein gets activated?

Answer 13

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

Question 14

What is the function of the Ras protein?

Answer 14

Activated Ras proteins transduce signals from the growth factor to signalling processes, thereby leading to cell division.

Question 15

What is the result of a mutation in ras gene?

Answer 15

It results in a constitutively active Ras protein, leading to increased cell division even when growth factor not binded to receptor

Question 16

What does the p53 gene code for?

Answer 16

It code for specific transcription factors, p53 protein.

Question 17

What does p53 protein do?

Answer 17

It binds to DNA to promote synthesis of cell cycle-inhibiting proteins, therefore p53 protein functions as an activator

Question 18

What is the normal role of p53 protein?

Answer 18

It upregulates expression of genes involved in:
- cell cycle arrest
- DNA repair
- (if DNA beyond repair) initiates apoptosis (cell death)

Question 19

What is the result of a mutation in p53 gene?

Answer 19

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.

Question 20

What are the number of alleles needed to be mutated for gain-in-function mutation to be cancerous?

Answer 20

Only one copy of allele needs to be mutated, known as dominant mutation

Question 21

What are the number of alleles needed to mutated for loss-in-function mutation to be cancerous?

Answer 21

Both copies of alleles need to be mutated, known as recessive mutation