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RACP 2023 > GENETICS > Flashcards

GENETICS Flashcards

1
Q

Features of autosomal recessive inheritance?

A
  • Not in every generation
  • if sibling has it: 2/3 chance of being a carrier, 1/4 not affected
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2
Q

Name some autosomal recessive diseases?

A

CF
Alpha 1 antitrypsin
Hemoglobinopathies: SCD, thalaessemia
Haemachromatosis
FMF
Friedrich’s ataxia
SMA
SCD
Kartagener
Homocystinuria

Inborn errors of metabolism
- Tay Sachs
- Wilson

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3
Q

Features of Autosomal Dominant diseases?

A

In every generation
50% chance of getting it if you’re a first degree relative; every degree away is 50% of that risk
All affected children have an affected parent

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4
Q

Name some autosomal dominant diseases?

A

PCKD
FH
Huntington
Myotonic dystrophy
Tuberous sclerosis
vWF
Malignant Hyperthermia
MND
Di George
Adrenoleukodystrophy

Cancer syndromes: BRCA, MEN, VHL, HNPCC
Genetic syndromes: Noon, Williams
Skeletal syndromes: Marfan, Achondroplasia, Ehlers Danlos
Cardiac: CM, Brugada,

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5
Q

Name some diseases caused by mosaicism?

A

Turner
NF1
Tuberous Sclerosis
DMD: gonadal
Achondroplasia: gonadal

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6
Q

What causes chimeric diseases?

A

SCT

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7
Q

Features of X linked recessive diseases?

A

Males affected more
If father affected: daughters carriers
If mother affected: 50% chance daughters are carriers/ 50% chance sons affected

NO MALE TO MALE TRANSMISSION

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8
Q

Name some X linked recessive conditions?

A

Muscular dystrophy: Duchenne, Becker
Hemophilia
CGD
G6PD
Fragile X
Fabry’s

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9
Q

Examples of X linked dominant conditions?

A

Alport
Rett

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10
Q

Examples of diseases with imprinting?

A

Prader Willi
Angolan

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11
Q

How can an imprinted disease cause disease?

A

Loss of imprinting
UPD
Mutation in expressed gene

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12
Q

Features of mitochondrial diseases?

A

Passed on from mother ONLY
Affects female and male children

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13
Q

Homoplasmy vs heteroplasmy; explain?

A

Mitchondrial disease affects ALL DNA: homoplasmy
Some DNA: heteroplasmy

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14
Q

What testing can be used for chromosomal variations? Adv and disadv for each?

A

All can do CNVs

Karyotype: not very small nucleotide variations
FISH: more accurate
Microarray/CGH: most accurate, can do microscopic deletions/duplications; NO TRANSLOCATIONS

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15
Q

What testing can be used for nucleotide variations? Disadvantage?

A

Sanger: Gold standard
Next gen sequencing

DISADV: no trinucleotide expansions

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16
Q

What testing can be used for trinucleotide expansions?

A

Triplet PCR
Southern Blot

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17
Q

What testing can be used for imprinting disorders?

A

Multiplex ligation dependent probe amplication: BEST
Methylation specific MLPA

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18
Q

What to do with VUS?

A

Doesn’t confirm dx, don’t use to make clinical decisions, don’t test unaffected relatives, don’t let affect family planning

Suspicious: further studies

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19
Q

What is lyonisation? What does it result in?

A

X inactivation (random)

Result
- X linked recessive diseases: females have milder/later phenotype

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20
Q

Features of XLD disease?

A

If father has affected X
- Sons unaffected
- All daughters get it

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21
Q

Features of XLR disease?

A

Transmitted through carrier females
- Males affected mostly (mother has to give X to all sons)
- Female carriers usually unaffected but CAN BE AFFECTED
- Affected males cannot transmit to sons

If mother is the carrier
- Daughters: 50% chance carrier
- Sons: 50% chance affected
If father has condition
- Daughters will be carriers (has to pass X to daughters)
- Cannot pass onto sons

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22
Q

Features of mitochondrial disorder?

A
  • Have their own extrachromosomal DNA
  • Inherited through maternal lineage
    • Passed onto ALL children
    • MALES AND FEMALES affected
    • Variable expressivity common
      ○ Children get different mutant load amounts
      • Males cannot transmit disorder
23
Q

Fragile X features?

Mode of inheritance?

A

Parkisonism
Cognitive impairment
Tremor
Mood disturbance
Ataxia

X linked dom
- CCG triplet repeat

24
Q

Examples of imprinting disorders?

A

Prader Willi

25
Q

Features of Prader Willi?

A

Obesity
Short
DD
Hypogonatrophic hypogonadism

26
Q

Tay Sachs features and transmission mode?

A

Young death

Lipids not broken down –> accumulate in brain

Autosomal recessive

27
Q

Tuberous sclerosis transmission mode and features

A

Autosomal dominant

Growths on scalp/ fingers/ gums/ brain/ lungs/ kidney

28
Q

Noonan Syndrome features and transmission mode?

A

Wide set nipples
Ptosis
Webbed neck
wide spaced and down slanting palpebral fissures
low set ears
Short and wifee nose
Delayed cognition
CHD: PS
Neoplasms

Autosomal dominant: PTPN11

29
Q

Features of NF 1 and 2? Mode of transmission?

A

NF 1
- Skin: cafe au lait, irish hamartomas, freckling
- Optic pathway glioma
- Pheochromocytoma/ renal vascular stenosis
- Breast cancer
- Peripheral n tumour
- Osseus lesion
- Family history

NF2
- Bilateral vestibular schwannomas

Autosomal dominant

30
Q

Marfans features?

A

Ectopia lentis
FBN-1 mutation
Aortic aneurysm
Wrist and thumb sign

31
Q

Differentials for Marfan’s?

A

Loeys Dietz: Arterial aneurysm, left palate, skeletal abnormalities, NO ECTOPIA LENTIS
Ehlers Danlos:

32
Q

Most common mutation defect causing dystropinopathies?

A

Exon deletion

33
Q

Difference between Duchenne and Becker?

A

Duchenne: absent
Becker: reduced

34
Q

Symptoms of Duchenne + Becker

A

Myopathy proximal > distal
calf hypertrophy
DCM/ HOCM
CK elevated

35
Q

Friedriche’s Ataxia features?

A

Cerebellar
Motor weakness
Sensory loss to propriception/ vibration
Hearing loss
Diabetes

PRESERVED COGNITION

36
Q

Spinocerebellar ataxia features?

A

Cerebellar
- progressive ataxia
- coordination
-dysarthria
- cognition dysfunction
- sleep
- younger onset

37
Q

Spinocerebellar ataxia mode of transmission?

A

Autosomal dominant
triplet repeat

38
Q

Di George Syndrome features?

A

Cardiac abnormality
Abnormal facies
Thymus aplasia
Cleft palate
Hypocalcemia
Chromosome 22

39
Q

Klinefelter genetic abnormality?

A

Extra X chromosome in a male

40
Q

How to diagnose Klinefelter’s genetic abnormality?

A

47XXY –> karyotype/ chromosomal microarray
48XXXY

41
Q

Features of Klinefelter?

A

Physical: small testes, gynaecomastia, infertility, low libido, genetic abnormalities
Learning delay
Metabolic syndrome
Hypothyroidism
Osteoporosis

42
Q

Turner’s syndrome genetic abnormality?

A

45 X, O

43
Q

Turner syndrome features?

A

Short stature
Cardiac: aortic coarctation/ bicuspid valve
Amenorrhea
Hypothyroidism
Primary ovarian failure

44
Q

Down’s syndrome genetic abnormality?

A

21 balanced translocation

45
Q

How to diagnose Down’s genetic abnormality?

A

FISH NOT CMA

46
Q

Most common cardiac defect in Down’s?

A

Endocardial cushions defect

47
Q

Haemochromotosis genes and mode of inheritance

A

Autosomal recessive

C282Y
H63D

48
Q

Diagnosis of haemachromotosis? WHat’s the earliest sign?

A

Transferrin: earliest sign
High ferritin
Low hepcidin
MRI: deposits

49
Q

Chromosome testing looks at cells in which phase?

A

Metaphase

50
Q

Effects of protein truncating mutation?

A

Hapolinsufficiency: 1/2 dose of protein

51
Q

Effects of mis sense mutation?

A

Gain of function

OR

Abnormal protein

52
Q

Cause of GOF mutations?

A

Switching back on of a gene which should be switched off after early life
Extra gene copies
Chromosome translocations -> enhanced gene expression

53
Q

LOF mutations: what do these genes usually do?

A

Repairs damaged DNA
Regulates cell division
Promotes apoptosis of damaged cells

54
Q

IHC testing:
- meaning of presence/absence?

A

Presence: normal
Absence: possibility of gremlin pathogenic variant

RACP 2023 (17 decks)

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