cancer

Question 1

what is cancer

Answer 1

a disease of uncontrolled cell proliferation and differentiation

Question 2

what experiment was used to show how infection affects development of cancer

Answer 2

1. sarcoma (cancerous cells) were taken from the breast muscle of an old chicken and injected into a young, healthy chicken
2. the young chicken developed dose-dependent sarcoma proving that it could be transferred between animals
3. the sarcoma contained a virus with a gene that controlled cell adhesion, proliferation and mobility
4. the virus encoded a hyperactive form of the gene that caused tumors

Question 3

how can diet affect the development of cancer

Answer 3

exposure to fungus tat can grow on rice and peanuts can increase the risk of cancer
the fungus releases toxins that mutate DNA

Question 4

how can noxious substances affect the development of cancer

Answer 4

asbestos causes cancer when breathed in as it causes fluid to build up in the lungs which can lead to tumors

Question 5

how can translocation of chromosomes affect the development of cancer

Answer 5

translocation can cause genes to fuse producing fusion proteins that lead to constant cell proliferation forming tumors

Question 7

what are oncogenes

Answer 7

mutated proto-oncogenes that can cause tumors to form

Question 8

what can cause oncogenes to form

Answer 8

mutation in the coding sequence of DNA producing large amounts of hyperactive protein
chromosome rearrangement producing large amounts of hyperactive protein
mutation in the regulatory area upstream of the gene producing large amounts of normal protein
gene amplification producing large amounts of normal protein

Question 9

how is the oncogene Ras switched between two states

Answer 9

when it is bound to GTP it is switched on and when it is bound to GDP it is off
another protein removes GDP from Ras causing it to change shape into the switched on form because there is more GTP
to turn it off Ras has intrinsic GTPase activity to remove GTP and convert it to the off form

Question 10

how do growth factors induce cell growth

Answer 10

1. growth factor binds to single subunits receptor tyrosine kinase (RTK) activating it and causing subunits to join forming dimers
2. the dimer self-phosphorylate and Grb2 and Sos bind to form a complex
3. Sos removes GDP from Ras switching it on causing cell growth

Question 11

what happens when Ras is mutated

Answer 11

if amino acids in Ras mutate the intrinsic GTPase activity is inhibited so Ras is constantly switched on and growth factors aren’t needed

Question 12

how do tumors evolve

Answer 12

1. random mutations in a cell can cause the cell to proliferate more
2. this mutation is selected so there is clonal expansion of this mutated cell
3. there are more cells with this genotype so the likelihood of mutations occurring increases

Question 13

why are cancer cells genetically unstable and what causes this

Answer 13

chromosomes in cancer cells have more translocation and chromosomal deletions which makes them more likely to mutate
this is caused by defects in DNA repair pathways and correction pathways

Question 14

what are the differences between oncogenes and tumor suppressor genes

Answer 14

in oncogenes a mutation causes them to be activated by a mutation in TSG inactivates them
oncogenes are an example of gain of function mutations and TSG are loss of function
oncogenes are dominant and TSG is recessive

Question 15

what is the role of P53 in the cell cycle

Answer 15

it can slow the cell cycle to allow DNA to be repaired and it can stimulate apoptosis to destroy faulty cells

Question 16

how does P53 affect the development of cancer

Answer 16

in cancer cells P53 is mutated so damaged cells keep dividing and aren’t destroyed