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Flashcards in Tumour pathology 4 Deck (41)
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1

What is cell cycle

Time interval between mitotic division

2

What is the timing for the cell cycle

G1- 8 hours
S- 10hr
G2-5hrs
M-hr

3

What is external factors in the cell cycle

Hormones, growth factors, cytokines, stroma

4

What is intrinsic factors in cell cycle

critical checkpoints - Restriction point (R)

5

prior to restriction point progress what does G1 depends

external stimuli

6

After restriction point what does the progression of the cell cycle become

autonomous - indépendant

7

What are the reasons G1 or G2 arrest the cell cycle

If cell size inadequate - G1 or G2 arrest
If nutrient supply inadequate - G1 arrest
Essential external stimulus lacking - G1 arrest
If DNA damage is detected - G1 or G2 arrest

8

when Mphase arrest the cell cycle

Chromosome mis-alignment - M-phase arrest

9

Where are the checkpoints in the cell cycle

G1 G2 M

10

What are checkpoints?

catalytic subunits are called cyclin-dependent kinases (CDKs) activated by regulatory sub-units called cyclins

11

What is the checkpoint active enzyme complex called

CDK/cyclin complex

12

How do CDK/cyclin complex work as check point mediators

phosphorylation of target proteins resulting in activation/inactivation of that substrate

13

What does the substrate do in the next phase of the cell cycle

Regulates events

14

What happens to cyclins in the cell cycle

accumulate and are destroyed by cell progress

15

How are CDKS expressed

inactive form

16

What two families of CDK inhibitors (CDKis) are important to checkpoints?

INK4A family and CIP/KIP family

17

How do CDK inhibitors work

Bind to CDK complex

18

What do active cyclin D/CDK complexes phosphorylate

pRb

19

What is hypophosphorylated pRbs function

bind to E2F

20

What happens when pRb is phosphorylated?

Becomes inactivated and looses its affinity for E2F, therefore free E2F can activate vital target genes stimulating cell cycle entry

21

What does active pRb act as

a brake in the cell cycle

22

What normal balance does carcinogeneis upset

Proliferation and apoptosis

23

Where can mutations occur to cause a cell to loose control of its proliferation

genes regulating cell division,
apoptosis,
DNA repair

24

What is the environmental agents causing cacinognesuis

Chemicals
Radiation
Oncogenic viruses

25

What is damaged in DNA by various oxidizing and alkylating agents

purine and pyrimidine bases

26

What is DNA adducts

Chemical carcinogens or their active metabolites react with DNA forming covalently bound products

27

What does adduct formation at particular chromosome site cause

cancer

28

High-energy radiation is carcinogenic if received in sufficient doses of what types of radiation

ultraviolet radiation (UV-B present in sunlight)
X-rays
Gamma radiation

29

What is the primary defect in cancer

Uncontrolled cell proliferation via
cell cycle dysregulation

30

What are the two regulatory pathways frequently disrupted in the cell cycle

The cyclin D-pRb-E2F pathway - G2 check point
p53 pathway - G1 checkpoint

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