Genetics Flashcards

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1
Q

What is the difference between a somatic mutation and a germline mutation?

A

Somatic mutation affects one cell in non-germline tissues and are non-heritable
Germline mutation affects cell in egg or sperm and is passed onto every cell in offspring, causing family cancer syndromes

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2
Q

What is an example of oncogenic cancer.

A

Oncogene ABL fuses sporadically with BCR, making BCR-ABL fusion protein and causes leukaemia

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3
Q

What is HNPCC?

A

Hereditary non-polyposis colorectal cancer
Mutation in mismatch repair genes
Adenoma-carcinoma sequence for polyp formation
AKA Lynch syndrome

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4
Q

Where do HNPCC tumours usually present?

A

Proximal colon

Often endometrial cancers for women

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5
Q

What are some options for breast surveillance?

A

Breast awareness
Annual or clinical exam
Mammography
MR screening for highest risk

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6
Q

What are the main genes tested for in breast cancer?

A
BRCA1
BRCA2
PALB2
PTEN
P53
CHEK2
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7
Q

What are the main genes tested for in ovarian cancer?

A
BRCA1
BRCA2
Lynch genes
RAD51C
RAD51D
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8
Q

What is a management option for BRCA1/2 carriers?

A

Prophylactic mastectomy

Significantly reduces risk

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9
Q

What are some drawbacks of prophylactic oophererctomy for primary ovarian cancer?

A

Peritoneal carcinomatosis may still occur

Induces surgical menopause

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10
Q

What are some options for surveillance of CRC?

A

Colonoscopy (Frequency depends on risk)

Prophylactic aspirin

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11
Q

What are some risks of genetic testing for familial cancers?

A

Does not detect all mutations
Continued risk of sporadic cancer
Efficacy of interventions variable
May result in psychosocial or economic harm

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12
Q

What are the 3 ways multi-system disorders can be inherited?

A

Chromosomal (Trisomy 21)
Single gene disorders (myotonic dystrophy, CF, Duchenne’s)
Multifactorial (diabetes)

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13
Q

Why do some mutations give multi-system disorders?

A

Single genes may have diverse functions
Single gene widely expressed in different tissues
Gene may be tissue specific but tissue is in many different systems

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14
Q

How does neurofibromatosis type 1 (NF1) present?

A
Cafe au lait spots
Neurofibromas
Axillary freckling
Lisch nodes
Optic glioma
Thinning of long bone cortex
Raised BP
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15
Q

Which gene causes NF1?

A

17q

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16
Q

What are the main features of NF2?

A

Acoustic neuroma
CNS and spinal tumour
CAL spots
NF2 gene is on chromosome 22

17
Q

What is the classic triad of Tuberous Sclerosis (TS)?

A

Epilepsy
Learning difficulty
Skin lesions

Myoclonic seizures

18
Q

Which genes cause TS?

A

TSC1

TSC2

19
Q

How are relatives at risk of TS screened?

A
Skin signs
Retinal exam
Cranial MR scan
Renal USS
Echocardiogram
20
Q

How does myotonic dystrophy present?

A
Bilateral late-onset cataract
Muscle weakness
Stiffness
Myotonia
Low motivation
Bowel problems
Heart block
21
Q

Why may an adult be referred for pre-symptomatic testing?

A
Diagnosis
Predictive testing
Carrier testing
Family history
Fetal loss or recurrent miscarriage
22
Q

Is risk estimation more difficult for single gene or multifactorial conditions?

A

Single gene

Especially those with high penetrance

23
Q

What is a requirement of testing for children and adolescents?

A

Must be some potential medical benefits

24
Q

What is mean age onset for MND?

A

55

25
Q

What are some clinical features of MND?

A

Progressive muscle weakness, wasting and increased reflexes
Pure motors signs with fasciculations
Cognition spared
Death due to respiratory failure

26
Q

What is another name for MND?

A

Amyotrophic lateral sclerosis

27
Q

What happens in MND?

A

Superoxide Dismutase

Catalysis of conversion of intracellular superoxide radicals

28
Q

Is Huntington’s disease usually youth or adult onset?

A

Adult

29
Q

How does HD affect movement?

A

Chorea
Athetosis
Myoclonus
Rigidity

30
Q

How does HD affect cognitive changes?

A
Poor planning and memory
Subcortical dementia (executive function)
31
Q

How does HD affect personality?

A
Irritable
Apathetic
Loss of empathy
Disinhibition
Self centred
32
Q

How does HD affect psychiatry?

A

Depression
Paranoia
Psychosis

33
Q

What are some disadvantages of a positive predictive test?

A

Less hope
Still uncertain with onset
Risk to offspring
Potential insurance/mortgage problems

34
Q

What are some advantages of a positive predictive test?

A

Uncertainty removed
Make plans for future
Arrange surveillance
Inform children or decide whether or not to have them

35
Q

What are some requirements for predictive testing?

A

Info must be useable for prevention or treatment
Require proper counselling
Children only tested if potential medical benefits
Third parties should have no access
Susceptibility testing requires adequate information about uncertainty

36
Q

What are some common features of down’s syndrome?

A
Flattened face
Almond shaped slanted eyes
Short neck
Small ears, hands and feet
White spots in iris
Tongue sticks out
Single palmar crease
Curved pinkies towards thumb
Poor muscle tone
Short
Small malleolus
37
Q

What are the main characteristics of Kallman syndrome?

A

Delayed or absent puberty

Impaired sense of smell