Genetics Flashcards

1
Q

What are some of the causes of hereditary susceptibility to colorectal cancer ?

A

Sporadic (65%)
Rare CRC Syndromes
Lynch syndrome
Familial

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2
Q

What are the 2 types of mutations which occur and can predispose people to cancer ?

A

Germaline mutations

Somatic mutations

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3
Q

Which type of mutations cause cancer family syndromes ?

A

Germaline Mutations

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4
Q

Which type of gene mutations are nonheritable ?

A

Somatic mutations

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5
Q

Where in the cell cycle do oncogenes contribute ?

A

After G1 (Cell growth)

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6
Q

Where in the cell cycle do tumor suppressor genes contribute ?

A

Between G0 and Synthesis (S)

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7
Q

Where in the cell cycle does DNA repair genes ?

A

Between synthesis and G2

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8
Q

How many mutations are need for cancer development ?

A

1 Mutation is sufficient for role in cancer development ?

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9
Q

In cancer what takes a normal epithelium to a hyper-proliferative epithelium ?

A

Loss of APC

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10
Q

In cancer what takes an early adenoma to an intermediate adenoma ?

A

Activation of K-ras

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11
Q

In cancer what takes an intermediate adenoma to a late adenoma ?

A

Loss of 18q

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12
Q

In cancer what takes a late adenoma to a carcinoma ?

A

Loss of TP53

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13
Q

What is the main mechanism for familial cancer ?

A

Faulty DNA mismatch repair

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14
Q

What is Lynch syndrome/Hereditary Non-Polyposis Colon Cancer ?

A

Mutation in mismatch repair genes

Excess of colorectal, endometrial, urinary tract, ovarian and gastric cancers.

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15
Q

What are the clinical features of Hereditary Non-Polyposis Colon Cancer ?

A

Early but variable age

Tumour site in proximal colon predominates

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16
Q

What areas in the body are cancer most likely in Lynch syndrome ?

A

Colon

Endometrial

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17
Q

What does autosomal dominant inheritance mean ?

A

Each child has 50% chance of inheriting the mutation

No skipped generations

Equally transmitted by men and women

18
Q

When should you suspect hereditary cancer syndrome ?

A

Cancer in 2 or more close relatives

Early age at diagnosis

Multiple primary tumors

Bilateral or multiple rare cancers

19
Q

What is the surveillance for colorectal cancer ?

A

Colonoscopy

20
Q

If you are a gene carrier for CRC how often should you surveyed ?

A

2x yearly from 25/35

21
Q

If you are moderate risk for CRC how often should you be surveyed ?

A

5 yearly from 50

22
Q

What are the benefits of genetic testing ?

A

Identifies highest risk.
Identifies non-carriers in families with a known mutation.
Allows early detection and prevention strategies.
May relieve anxiety.

23
Q

What are the risks and limitations of genetic testing ?

A

Does not detect all mutations.
Continued risk of sporadic cancer.
Efficacy of interventions possible.
May result in psychological or economic harm

24
Q

Name forms of chromosomal defects

A

Numerical i.e. Trisomy 21

Structural i.e. Translocations, deletions and microdeletions

25
Q

Name forms of single gene disorders

A

Autosomal dominant i.e. Myotonic Dystrophy.

Autosomal recessive i.e. CF.

X-linked i.e. Duchenne muscular dystrophy

26
Q

What are the features of Neurofibromatosis Type 1 (NF1) ?

A

Autosomal dominant

Macroencephaly
Short stature
Dysmorphic features
Learning difficulties
Epilepsy
Scoliosis 
Hypertensive (Renal artery stenosis)
27
Q

What criteria is used to diagnose NF1 ?

A

NIH criteria (need 2+ for diagnosis)

28
Q

What gene has been identified in NF1 ?

A

17q

29
Q

What are the main features of NF2 ?

A

Acoustic neuromas

CNS and spinal tumors

30
Q

Where is the NF2 gene ?

A

On chromosome 22

31
Q

What is the classical triad found in those with Tuberous Sclerosis ?

A

Epilepsy
Learning difficulties
Skin lesions

32
Q

What are the features of Myotonic Dystrophy ?

A

Autosomal dominant

Bilateral late-onset cataract
Muscle weakness, stiffness and myotonia.
Diabetes.
Heart block.

33
Q

What are the clinical features of ALS?

A

Progressive muscle weakness, wasting and increased reflexes.

Limb and bulbar muscles involved.

Pure motor signs (fasiculations)

Cognition speed.

Death due to resp. failure

34
Q

In humans, three forms of superoxide dismutase are present, where is SOD1 located ?

A

Cytoplasm

35
Q

Where in humans is SOD2 located ?

A

Mitochondria

36
Q

Where in humans is SOD3 located ?

A

Extracellular

37
Q

Where are the genes fro SOD 1, 2 and 3 located ?

A

Chromosomes 21, 6 and 4

38
Q

What does the presence of SOD do for the body ?

A

Protects many types of cell from free radical damage that is important in ageing and ischaemic tissue damage.

39
Q

What is the unique mutation identified in huntington’s disease ?

A

CAG expansion

40
Q

What are the clinical features of huntingtons ?

A
Movement disorder
Chorea
Athetosis
Myoclonus
Rgidity

Onset early 30s/40s