Tumours Pt 3

Question 1

What are the 6 phases of the cell cycle?

Answer 1

Interphase, Prophase, metaphase, anaphase, telophase and cytokinesis

Question 2

What are the phases within interphase?

Answer 2

G1 (growth)
S-phase (dna synthesised)
G2 (rapid growth)
M-phase (mitosis)

Question 3

Where are the barriers in the cell cycle?

Answer 3

End of G1
G2 - M phase barrier

Question 4

What is the purpose of barriers/ checkpointsin the cell cycle?

Answer 4

G1 = if there aren’t adequate nutrients
G2 - M = If DNA is mutated, prevents replication. Way to avoid cancer

Question 5

What indirectly causes G1 to be pushed to restriction point?

Answer 5

Growth factors bind to receptors outside cell which lead to series of events

Question 6

How does phosphate affect G1 reaching threshold?

Answer 6

Hyper-phosphorylation of RB means it is released from E2F, which can bind to promoters and activates cycle

Too little phosphate means RB is still bound to E2F, and cycle cant occur

Question 7

What conditions must the body be in to be able to phosphorylase retinoblastoma?

Answer 7

Amino acids and glucose (nutrients) needed for protein kinase to function

Question 8

What is Retinoblastoma gene product?

Answer 8

A protein product and tumour suppressor

Switch for E2F

Question 9

What is the role of a tumour-suppressing gene?

Answer 9

Control proto-oncogenes and replication of cells

Question 10

How can DNA be damaged (2) and which proteins assist in the repair process?

Answer 10

Radiotherapy or chemotherapy can cause is matched base pairs - mutation

MLH1 is released. This induces p53 to stop cell cycle so mismatch can be repaired

Question 11

What is a de-novo mutation?

Answer 11

Mutation of child due to prescience of mutated germ cell (egg or sperm) in adult

This is an inherited example of carcinogenesis

Question 12

What are 3 examples of environmental factors of carcinogenesis? How does it link to genetics?

Answer 12

Smoking, (chemical), Radiation (UV sun) or infection (HPV)

Increased risk of carcinogenesis in those with certain inherited genes

Question 13

What is the multi-step nature of carcinogenesis?

Answer 13

Mutated gene passes……

Question 14

What is HER-2 and its role?

Answer 14

Growth factor that binds as ligand to external receptor ad triggers cell cycle to occur

Question 15

What is BRAF? What can it cause if mutated?

Answer 15

Porto-oncogene. If common mutation occurs, switching glutamic acid to valine, BRAF converts to BRAF V600. This pushes cell cycle all the time

Can cause malignant melanoma if mutated

Question 16

What is MLH1 and its role?

Answer 16

Protein which can stop cell cycle to repair mismatched genes. Induces p53

Question 17

What is p53 and its role?

Answer 17

Protein triggered by MLH1, which can stop cell cycle while repair occurs

Question 18

How can environmental factors cause HPV?

Answer 18

Infection in cervix produces E6, which inactivates p53 so mutations in DNA aren’t corrected and cells divide

Question 19

How can smoking lead to cancer?

Answer 19

Chemicals metabolised in liver, and carcinogens may be released in blood. These could mutate p53 and lead to proliferation and damaged DNA not being repaired

Question 20

How can excess alcohol lead to carcinogenesis?

Answer 20

Too much cant be metabolised in liver. Converted to acetaldehyde which enters circulation and breaks DNA double bonds, allowing opportunity for mismatch