2.7: cancer

Question 1

(causative factors) genetics

Answer 1

defective alleles inherited from parents

increased predispositions to cancer

Question 2

normal RB gene function

Answer 2

halts cell cycle in absence of growth factors

Question 3

mutated RB gene

Answer 3

loss or RB activity

allows proliferation in absence of growth factors

Question 4

normal p53 gene function

Answer 4

prevents cells with dmg DNA from proliferating

Question 5

mutated p53 gene

Answer 5

damaged cells continue to divide

Question 6

normal BRCA1, BRCA2 gene function

Answer 6

repair of DNA double strand breaks

Question 7

mutated BRCA1, BRCA2 gene

Answer 7

inability to repair breaks

increased risk of ovarian and breast cancer

Question 8

types of chemical carcinogens

Answer 8

tar, EtBr

Question 9

how do chemical carcinogens cause cancer

Answer 9

1. covalent bonds w DNA -> DNA-carcinogen complex
2. distorts DNA double helix
3. replication errors
4. removing nucleotides
5. DNA strand breakage

Question 10

types of ionising radiation

Answer 10

X-rays, gamma rays, UV rays

Question 11

how does ionising radiation cause cancer

Answer 11

1. high energy
2. breaks in DNA backbone / formation of pyrimidine dimers
3. permanent base change

Question 12

types of infectious agents

Answer 12

HIV, HPV

Question 13

how do infectious agents cause cancer

Answer 13

1, integrate genetic material into human DNA
2. days regulation of cell cycle checkpoints
3. uncontrolled proliferation of dmg DNA cells

Question 14

what is a proto oncogene?

Answer 14

genes coding for proteins that

promote normal cell growth and division

Question 15

what is a tumour suppressor gene?

Answer 15

genes coding for proteins that

normally inhibit cell division

cell cycle arrest, DNA repair, blocking angiogenesis and apoptosis

Question 16

what is a gain in function mutation

Answer 16

proto-oncogene -> oncogene
- increase in amt of protein produced
- hyperactivity of protein

eg Ras gene

Question 17

how many alleles needed to undergo GOF mutation

Answer 17

1

Question 18

loss in function mutation

Answer 18

• accumulation of mutations
• excessive cell growth and divisions

eg p53 gene

Question 19

how many alleles need to undergo LOF mutation

Answer 19

2

Question 20

why is it relatively difficult to develop cancer?

Answer 20

1. proofreading mechanisms check and repair mutations
2. cells w irreparable mutation undergo apoptosis via p53
3. only mutations in PO or TSG will lead to cancer
4. all mutations must occur in a single cell for cancer to form

Question 21

what is the multi step model of cancer?

Answer 21

1. GIF of PO
2. LOF of TSG
3. evasion of apoptosis
4. activation of telomerase gene
5. angiogenesis
6. metastasis and tissue invasion

Question 22

activation of telomerase

Answer 22

• cancer cells activate
• add new copies of telomeric repeat seq
• telomeres do not shorten
• cells divide infinitely

limitless replicative potential

Question 23

what is angiogenesis

Answer 23

formation of blood vessels

supplies nutrients to cancer cells

remove toxic waste

blood vessels provide a route to the rest of the body for metastasis

Question 24

describe how dysregulation of checkpoints of cell div may result in cancer

Answer 24

1. M checkpoint dysregulation
   - cells enter anaphase despite improper attachment of spindle fibres of chromosomes at metaphase
   - non-disjunction -> daughter cells with extra copies of proto-oncogenes
2. G1/G2 checkpoint dysregulation
   - unrepaired dmg DNA being passed on to daughter cells

dysregulation allows cells w improper structures to enter next cell cycle phase
replicate = uncontrolled and excessive cell division = cancer