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Conditions + definitions > Genetics > Flashcards

Genetics Flashcards

1
Q

What is nonsense mediated decay?

A

Getting rid of proteins produced that don’t conform to normal standards (either stop being too early or too late)

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2
Q

What is polygenic risk?

A

Multiple genes contributing towards familiar risk

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3
Q

What is leucocornea?

A

White eye in retinoblastoma

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4
Q

What happens in hereditary non-polyposis colon cancer? (HNPCC/lynch syndrome)

A

Mutation in mistmatch repair genes
Excess of cancers in adenoma carincoma sequence
Early CRC
Effects proximal colon

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5
Q

What is a germline mutation?

A

Where mutation is present in egg/sperm and are henceforth heredtary
Cause cancer family syndromes

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6
Q

What is an oncogne?

A

A gene that controls cell processes that, if it mutates, will be enough to start the cancer process

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7
Q

What are the lifetime cancer risks of the BRCA genes?

A

Breast - 60-80% (early onset)
Secondary primary breast cancer - 40-60%
Ovarian 20-50%
Increased risk of prostate + breast cancer in men

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8
Q

When do you suspect hereditary cancer syndrome?

A 
Cancer in 2+ relatives
Early age of diagnosis
Multiple primary tumours
Bilateral or multiple rare cancers
Charactersitc pattern of tumours
Evidence of autosomal dominant transmission
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9
Q

What are the options for breast cancer surveillance?

A

Early clinical surveillance 5yrs before 1st cancer in family
Annual clinical breast exams
Mammography Every 2 yrs from 35-40, yearly from 40-50
Every 18 months if high risk from 50

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10
Q

What is the benefit of a prophylatic oophrectomy?

A

Eliminates risk of primary ovarian cancer (peritoneal cancers can still occur)
Risk of subsequent BRCA halved

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11
Q

How is colorectal cancer surveyed in lynch syndrmoe?

A

Colonoscopy every 2 years from 25 if high risk

If moderate risk once at 35 and once at 55

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12
Q

How is endometrial cancer screened for in lynch syndrome?

A

Transvaginal ultrasound

No recommendations

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13
Q

What are the limitations of genetic testing?

A

doesn’t detect all mutations
Continued risk of sporadic cancer
Efficacy of interventions variable
May result in psychosocial/economic harm

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14
Q

What cancers are associated with Li-Fraumeni syndrome?

A 
Soft-tissue sarcoma
Osteosarcoma
Breast cancer
Brain/CNS tumours
Adrencortical carcinoma
Acute luekemia
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15
Q

What are the modes of inheritance for multi-system disorders?

A 
Any possible
eg -
Chromosomal
Single gene
Poly gene
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16
Q

What are some important multi-system disorders?

A 
NF1
	Myotonic dystrophy
	Tuberous clerosis
	CF
	Downs
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17
Q

How do disorders cause mlti-system involvement?

A 
As several (or just one) gene with diverse functions are involved
This can be widely expressed in different tissues
>However expression in tissues can be different
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18
Q

What are the mechanisms of adult onset genetic disease?

A

Single gene
Chromosomal
Mitochondrial
Multifactorial

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19
Q

What are some common problems in multi-system disease?

A

Variable expression within + between families
Present to a large number of specialists
FH easily missed

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20
Q

What gene pattern is neurofibromatosis type 1 (NF1)?

A

Autosomal dominant

17q tumour supressor gene affected

21
Q

What is the diagnostic criteria for NF1 (neurofibromatosis type 1)?

A 
2+ of:
café au lait spots - 6 or more
neurofibromas - 2 or more
axillary freckling
Lisch nodules (specks in iris) 
optic glioma
thinning of long bone cortex
family history
22
Q

What other features can accompany NF1?

A 
Macrocephaly
Short sature
Dysmorphic features
Learning difficulties
Epilepsy
Scoliosis
Raised BP
Neoplasia
23
Q

How do you manage NF1?

A 
Annual review of affected individuals + at risk children until diagnosis excluded
Check for:
BP
Spine for scoliosis
Tibia for unusua angulation
Visual acuity/fields
Educational assesment
24
Q

What are the main features of NF2?

A

Acoustic neuromas (often bilateral)
CNS + spinal tumours
A few CAL spots

25
Q

WHat chromosome is NF2 found on?

A

Chromosome 22

26
Q

What is tuberous sclerosis?

A

An autosomal dominant disease with a triad of:
Epilepsy
Learning difficulty
Skin lesions

27
Q

What is the penetrance of tuberous sclerosis?

A

Almost full penetrance

28
Q

What genes cause TS?

A

TSC1

TSC2

29
Q

What are the clinical features of TS?

A 
Has variable expression
Learning difficulty common
Seizures common - infantile spasms, myoclonic seizures
Skin lesions
Kidney cysts
Phakomas in eyes
Rhabdomyomas in heart
30
Q

What are the skin lesions in TS?

A 
depigmented macules
angiofibromas
fibrous plaque forehead
shagreen patches 
ungual fibromas
31
Q

How do you screen relatives for TS?

A

Cranial MR scan
Renal USS
Echocardiogram
Clinical examination

32
Q

What is myotonic dystophy?

A

An autosomal dominant disease

Increases in severity with each generation

33
Q

What are the main symptoms of myotonic dystrophy?

A 
Bilateral late-onset cataract
Muscles weakness, stiffness + myotonia
Low motivation
Heart block
Congneitcal motonic dystrophy - can lead to death
34
Q

Why is risk estimation more difficult in multifacotrial conditions?

A

Often polygenic component interacting with environmental factors
Penetrance may vary
>Even if risk allele determined may no have disease

35
Q

What is penetrance?

A

The chance of having a genetic disease if you have the genes responsibile for it

36
Q

What is the mean age of onset for amyotophic lateral sclerosis?

A

55years (can be younger in familial forms)

37
Q

What are the clinical features of ALS?

A 
Progressive muscle weakness, wasting + increasing reflexes
>Upper + lower motor signs
Limb + bulbar muscle involvements
Pure motor signs with fasiculations
Cognition spared
Death eventually due to resp failure
38
Q

What is the only identified gene that causes ALS (accounts for only 2% of cases)?

A

Copper/zinc superoxide dismutase (SOD) mutations

39
Q

Where are SOD 1, 2 and 3 located?

A

SOD1 in cytoplasm
SOD2 in mitochondria (manganese)
SOD3 in extracellular

40
Q

What chromosomes are SOD genes located?

A

21
6
4

41
Q

What is the function of SOD?

A 
Protects cells from free radical damage
As well as protecting from DNA damage, 
Ionising radiation damage
Protein denaturation
Lipid peroxidation
42
Q

What is the penetrance of ALS?

A

Incomplete

43
Q

What is the prognosis of ALS?

A

As there is no cure or satisfactory treatment, pretty poor

44
Q

What are the symptoms of Huntington’s?

A 
Poor planning + memory
Subcortical dementia
Not classical dementia
Personality changes
Psychiatric disease - depression, paranoia, psychosis
45
Q

When does huntingtons present?

A

Onset late 30s-40s but variable

46
Q

What is the penetration of Huntingtons?

A

Fully penetrant

47
Q

What are the disadvantages of predictive testing (positive outcome)?

A 
Removes hope
Continues uncertainty (when, not if)
Known risk to offspring
Impact on self/family/friends
Potential problems with insurance/mortgage
48
Q

What are the disadvantages of predictive testing if negative result?

A

Survivour guilt

Expectations of a “good” result

49
Q

Do you test children for Huntingtons?

A

No.
As only 25% of people choose to be tested overall, testing a child would take away their right to not know if that was their wish

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