Week 9

Question 1

Why do cells divide?

Answer 1

• Healing and tissue repair
• Growth
• Reproduction of unicellular organisms

Question 2

What are the 4 phases of the cell cycle?

Answer 2

M - Mitosis
G1 - Primary growth
S - Synthesis phase (DNA replicated)
G2 - Secondary growth

Question 3

What happens in the G1 phase?

Answer 3

• Cells grow in preparation for DNA replication in S phase
• Organelle duplication
• Duration is variable - short in embryonic and cancer cells
• Cells that remain in G1 for a long time = G0 (permanent tissues, such as neural tissue)

Question 4

What happens in S phase?

Answer 4

• DNA and centrosome replication

- Cells committed to go through cell division once the S phase starts

Question 5

What happens in G2 phase?

Answer 5

• Cell growth continues
• Enzymes and proteins for cell division are synthesised
• Cell division machinery begins to assemble

Question 6

How is the cell cycle regulated?

Answer 6

• External regulation eg. growth factor signalling

- Internal checkpoints

Question 7

What are the internal checkpoints in the cell cycle?

Answer 7

• G1 checkpoint - DNA integrity, cell size and protein levels assessed
• G2 checkpoint - successful chromosome replication and no DNA damage
• M checkpoint - correct attachment of sister chromatids to spindle microtubules

Question 8

What are some positive regulator molecules of the cell cycle?

Answer 8

Cyclins and cyclin-dependent kinases

Cyclin-dependent kinases are activated by interacting with the regulatory subunit cyclin

Question 9

What are some negative regulator molecules of the cell cycle?

Answer 9

Rb, p53 and p21

Question 10

What happens at the G1 checkpoint?

Answer 10

• Main checkpoint that commits a cell to division
• Sensitive to: cell size, nutrients, growth factors and DNA damage
• Cyclin D-cdk complex drives cell through G1 to S phase

Question 11

What happens at the G2 checkpoint?

Answer 11

• Checks to see whether DNA replication is completed
• If any unreplicated DNA is detected, cells held at G2
• If damaged DNA detected, cells held in G2 until DNA

Question 12

What is a mitotic promoting factor?

Answer 12

Cyclin B/Cdk1

Question 13

What happens at the spindle assembly checkpoint (M checkpoint)?

Answer 13

• Prevents cells entering anaphase until all chromosomes are properly attached to the spindle
• Sensor for correct chromosome attachments are in the kinetochores

Question 14

What does p53 do?

Answer 14

p53 is a tumour suppressor gene

• p53 introduces a temporary cell cycle arrest to allow DNA damage to be repaired
• If damage cannot be repaired –> programmed cell death (apoptosis)
• Mutation in p53 –> cell checkpoint no longer works –> cells replicate damaged DNA and acquire many mutations

Question 15

What are the two basic components of tumours?

Answer 15

1) Parenchyma: neoplastic cells. Determines the biological behaviour of the neoplasm and the name of the neoplasm.
2) Reactive stroma: connective tissue, blood vessels, the supporting tissue. Determines growth and spread of tumour

Question 16

What is a carcinoma?

Answer 16

Epithelial neoplasm

Question 17

What is a sarcoma?

Answer 17

Connective tissue neoplasm

Question 18

What are the differences between a benign tumour and a malignant tumour?

Answer 18

Benign:

• No local invasion
• No metastasis
• Retain function
• Variable growth rate, often low

Malignant:

• Locally invasive, infiltrate
• Frequently metastasise
• Lose function
• Variable growth rate, grow more rapidly

Question 19

What does differentiation (in cancer cells) mean?

Answer 19

• Refers to the extent to which the neoplasm looks and functions like the parenchymal cells they are differentiating towards
• Most malignant neoplasms are graded as well (grade 1), moderately (grade 2) or poorly (grade 3) differentiated.
• Undifferentiated (anaplasia) reflects a total lack of differentiation and absence of specialisation

Question 20

What are the sampling approaches for diagnosis of tumours?

Answer 20

1) Excision
2) Biopsy: needle core/punch
3) Fine-needle aspiration
4) Cytologic smears (blood/bone marrow/ascitic & pleural fluid/ urine/ stool)

Question 21

What is the tumour regression grade used for?

Answer 21

Determines prognosis after treatment

TRG1 - TRG5

Question 22

What cancers are people with Lynch syndrome more at risk of developing?

Answer 22

• Colorectal cancer
• Endometrial cancer
• Stomach cancer
• Ovarian cancer

Question 23

What is relative risk reduction?

Answer 23

The reduction of risk in the intervention group relative to the risk in the control group

Question 24

What is absolute risk reduction?

Answer 24

The difference between risk in the intervention and control group

Question 25

What is number needed to treat?

Answer 25

The number of patients who need to be treated to prevent one additional adverse outcome

Question 26

How do you calculate Relative Risk Reduction?

Answer 26

(Control group event rate - experimental group event rate) / control group event rate

Question 27

How do you calculate Absolute Risk Reduction?

Answer 27

Control event rate - experimental event rate

Question 28

How do you calculate the Number Needed to Treat (NNT)?

Answer 28

1/ Absolute Risk Reduction

or

1/ CER - EER

Question 29

What are the Ottawa ankle rules?

Answer 29

Malleolar pain + any of the following:

1) Boney tenderness on lateral or medial malleolus
2) Inability to weight bear

Question 30

What do different T-score values mean?

Answer 30

Normal: greater than or equal to 1.0
Osteopenia: between -1.0 and -2.5
Osteoporosis: less than -2.5

Question 31

What is the gold standard for investigation of osteoporosis/osteomalacia?

Answer 31

DEXA scan