Topic F2

Question 1

What is an oncogene?

Answer 1

• A mutation in one or more copies of a proto-oncogene that causes a gain function mutation that causes the cancer cell to grow and divide inappropriately

Question 2

What is a proto-oncogene?

Answer 2

• Normal cellular genes that promote cell growth and cell division
• oncogenes are mutated forms of proto-oncogenes that lead to an increased activity of gene products

Question 3

What are the 3 main ways a proto-oncogene can become an oncogene?

Answer 3

• An activating mutation in a DNA coding sequence e.g. an overactive protein
• Gene amplification e.g. over-expressed receptors
• Chromosome re-arrangement: can produce fusion proteins that are over produced and highly oncogenic

Question 4

Are oncogenes dominant or recessive?

Answer 4

• Dominant; a single copy of the mutated cancer gene can predispose cancer by a gain of function mutation

Question 5

Can viruses mutate host proto-oncogenes to oncogenes?

Answer 5

Yes, the proto-oncogene may be altered following the insertion of the viral gene either upstream of the proto-oncogene or within the coding sequence e.g. papillomavirus causes cervical cancer

Question 6

What is the largest group of oncogenes?

Answer 6

• Tyrosine kinase receptors that are mutated or over expressed can cause cellular transformation (cancer)

Question 7

What are some examples of oncogenes

Answer 7

• PDGF
• Erb-B
• K-ras
• c-myc
• N-myc