Photocarcinogenesis

Question 1

what is a proto-oncogene?

Answer 1

the normal, unmutated form of an oncogene

Question 2

what is an oncogene

Answer 2

over-active form of a gene that positively regulates cell division

Question 3

what is a tumour suppressor?

Answer 3

inactive/non-functional form of a gene that negatively regulates cell division

Question 4

do tumour suppressor genes use a negative or positive feedback mechanism

Answer 4

negative

Question 5

example of an oncogene?

Answer 5

Ras
Raf
growth factor receptors

Question 6

example of a tumour suppressor gene?

Answer 6

Rb

Tp53

Question 7

what happens to proto-oncogenes to promote cell division and proliferation?

Answer 7

growth factor binds to GF receptor
GDP--> GTP
switches Ras ON
Binds to Raf
Cell division etc etc

Question 8

what happens when oncogenes to cause cancer?

Answer 8

Ras is constantly switched on

Question 9

3 jobs of p53 to prevent cancer?

Answer 9

Halts faulty cells at G1 checkpoint
DNA repair activated
Apoptosis triggered

Question 10

Most likely skin cancer you would get from long term sun exposure?

Answer 10

SCC

Question 11

Most likely skin cancers you would get from intense intermittent sun exposure eg holiday

Answer 11

1. Melanoma

2. BCC

Question 12

Most likely skin cancer you would get from sunbeds?

Answer 12

SCC

Question 13

What kind of immunosuppressing conditions heighten melanoma risk?

Answer 13

Crohn’s (80%)
UC (23%)
Organ transplantation

Question 14

Which kind of UV exposure causes direct DNA damage?

Answer 14

UVB

Question 15

which kind of UV exposure causes indirect DNA damage?

Answer 15

UVA

Question 16

what mutations occur as a result of UVB damage?

Answer 16

pyrimidine dimer (TT -> CC)

Question 17

How is direct DNA damage repaired?

Answer 17

nucleotide excision repair

Question 18

How indirect DNA damage repaired?

Answer 18

base excision repair

Question 19

Most common mutation in indirect DNA damage?

Answer 19

C->A point mutation

Question 20

how can UV damage cause immunosuppression

Answer 20

less langerhans cells,

uv-induced generation of T cells will have immunosuppressive activity

Question 21

Most common mutation in BCC?

Answer 21

PTCH1

Question 22

Most common mutations causing melanoma?

Answer 22

Ras, Raf, MAPK