Cancer genetics

Question 1

What is cancer?

Answer 1

(aka tumour/neoplasia) is a genetic disease => accumulation of mutations => Uncontrolled growth abnormal cells

Question 2

What is the difference between a benign and malignant tumor?

Answer 2

Benign: non-invasive & localised
Malignant: invasive & can metastasis

Question 3

What does cancer metastasis mean?

Answer 3

Cancer (tumour) which can move/spread away from 1º site and invade another (2º) site

Question 4

What is a tumor suppressor gene? How does it work?

Answer 4

Are genes which inhibit cells w/ mutations from becoming cancerous by:

• stopping proliferation to allow DNA repair mechanisms to fix mutated DNA (if damage is small)
• inducing apoptosis if damage is large

Question 5

Which part/s of the cell cycle are critical checkpoints for cancer? (3)

Answer 5

• G1/S checkpoint: allow time to repair damage
• S-phase: delay replication to “ “ “ “ “
• G2/M: (same as G1/S)

Question 6

What are the internal and external factors that can cause cancer?

Answer 6

• Int.: Faults in DNA repair mechan.; inherited mutation; epigenetic factors
• Ext.: Chem. mutagens; radiation; Infection (e.g. viral)

Question 7

Differentiate between a proto-oncogene and an oncogene?

Answer 7

• Proto-: genes which are responsible for normal cellular functions (e.g. produce a protein/hormone)
• Oncogene: mutated genes => overexpress proteins = loss of growth control => development of cancer (e.g. upregulation of protein/hormone)

Question 8

What is a c-onc? What is a v-onc?

Answer 8

C-onc: cellular oncogene- means the mutated gene remains in cell’s DNA
V-onc: refers to the mutated gene being incorporated in the virus

Question 9

How did scientists discover what caused cancer?

Answer 9

(Peyton) Rous injected cell-free extracts of tumour to healthy chicken -> developed cancer
=> cancer transmitted by virus (carried cancer gene)

Question 10

• Three ways an RNA tumor virus can cause cancer.

Answer 10

1. virus integrates RNA (tumour) in host cell’s chromo. (provirus) & replicates
2. 3.

Question 11

*Differentiate between a DNA tumor virus and an RNA tumor virus.

Answer 11

DNA: DNA (genome) in virus
RNA: RNA (genome) in virus
directly causing cancer

Question 12

*How do DNA viruses cause cancer?

Answer 12

1. Replication of viral genome in the host’s nucleus
2. Transcribe genes
3. cell down-regulates apoptosis & proliferate = cancer

Question 13

*Which point mutation causes a proto-oncogene to become an oncogene for KRAS? What affect does this mutation have?

Answer 13

Substitution (missense mutation) => change AA = change structure & function of protein

Question 14

How p53 is activated, and the effect this has.

Answer 14

• defects in repair
• damage in DNA-damage checkpoint
  => p53 protein activated => introduce apoptosis

Question 15

How p53 is inactivated, and the effect this has.

Answer 15

Both copies in the segments of 2 chromo. are missing (homozygous) => cancer cells proliferate

Question 16

How does retinoblastoma (RB) protein regulate the cell cycle? At which part of the cell cycle does this occur?

Answer 16

“regulates cell proliferation by restricting cell cycle progression at… G1” *(cite)

Question 17

What causes sporadic retinoblastomas?

Answer 17

2 separate mutations need to be introduced in the same gene of 2 chromo. (homozygous)

Question 18

*What is apoptosis? Which cellular processes are involved?

Answer 18

is programmed cell death. Cellular processes involved*

Question 19

Which enzymes cause apoptosis?

Answer 19

RB & p53 proteins

Question 20

What are the 2 tumour-associated antigens?

Answer 20

• Tumour-specific: only tumour cells have antigen bc overexpressed (silenced in normal cells)
• Tiss. differentiation: both normal & tumour tissue have it but it’s over exbressed in tumour cells

Question 21

What does p53 do?

Answer 21

translation factor > activates expression of proteins for cell regulation & apoptosis