Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

3. Week 1 - Medical Genetics > Commoner (non-cancer) genetic disorders > Flashcards

Commoner (non-cancer) genetic disorders Flashcards

(66 cards)

Start Studying
1
Q

What is the average onset for Huntington disease?

A

between 30-50 years

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the symptoms of Huntington disease?

A
  • progressive chorea
  • dementia
  • psychiatric symptoms
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is chorea?

A

involuntary movements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the inheritance pattern of Huntington disease?

A

Autosomal dominant with genetic anticipation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What gene is implicated in Huntington disease?

A

Huntingtin (HTT)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What mutation is present in Huntington disease?

A

unstable length mutation in HTT gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens to the length mutation in HTT?

A

Mutation length prone to expansion during meiosis, especially from the father

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the clinical relevance of the number of repeats in the HTT gene?

A

<35 repeats = unaffected
36-39 repeats = incomplete penetrance
>40 repeats = affected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the genetic code of the repeat unit in HTT?

A

CAG repeat unit - encodes polyglutamine tract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the physiological outcome of expansion of the tract in Huntington disease?

A

Expansion causes insoluble protein aggregates and neurotoxicity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the treatment options for Huntington disease?

A

No cure

DNA testing possible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

When would DNA testing be used for Huntington disease?

A
  • testing unaffected family members

- presymptomatic test (predictive)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the inheritance pattern of myotonic dystrophy?

A

Autosomal dominant with genetic anticipation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the symptoms of myotonic dystrophy?

A
  • progressive muscle weakness in early adulthood
  • myotonia
  • cataracts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the genetic basis of myotonic dystrophy?

A

unstable length mutation of a CTG repeat in the transcribed but not translated region of the DMPK gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which gene is implicated in myotonic dystrophy?

A

DMPK gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the clinical relevance of the length mutation for myotonic dystrophy?

A
  • Normal = 4-37 repeats
  • Affected = 50- >2000 repeats

N.B general correlation between number of repeats and clinical severity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the pathogenic mechanism in myotonic dystrophy?

A

Abnormal DMPK mrna indirectly affects adjacent genes, making their products appear reduced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Give examples of genes affected by a mutation in DMPK

A
  • chloride channel 1 gene
  • SIX5
  • DMWD
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the inheritance pattern of cystic fibrosis?

A

Autosomal recessive inheritance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the carrier frequency of cystic fibrosis?

A

1 in 20-25

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the clinical manifestations of cystic fibrosis?

A
  • recurrent lung infections with bronchiectasis and obstructive lung disease
  • exocrine pancreatic insufficiency
  • male infertility
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How is cystic fibrosis diagnosed?

A
  • newborn screening
  • genetic testing
  • sweat test
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How is newborn screening used to diagnose cystic fibrosis?

A

looking for elevated immunoreactive trypsin (IRT) level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
How is genetic testing used to diagnose cystic fibrosis?
Looking for common genetic mutations
26
How is sweat testing used to diagnose cystic fibrosis?
Increased concentration of chloride on two occasions
27
What is the underlying cellular abnormality in cystic fibrosis?
defective chloride ion channel resulting in increased thickness of secretions
28
Which gene is responsible in cystic fibrosis?
Cystic fibrosis transmembrane conductance regulator (CFTR)
29
What are the chances of a sibling of someone affected with cystic fibrosis being a carrier?
2 in 3
30
What is the most common mutation found in the CFTR gene?
F508del N.B - over 1000 different mutations known
31
What affect does the F508del have?
- in frame deletion of phenylalamine | - prevents the normal folding of a protein and insertion into the plasma membrane
32
What is cascade screening?
indentification of mutations permits prenatal diagnosis if desires and the subsequent identification of carrier relatives
33
What is the inheritance pattern of neurofibromatosis type 1?
Autosomal dominant inheritance
34
What is affected in neurofibromatosis type 1?
Typically cells derived from the neural crest - melanocytes - bone - connective tissue - neurons
35
What are the common features of neurofibromatosis type 1?
- cafe au lait macules - neurofibromas (from teens) - short stature - macrocephaly - learning difficulties (in 30%) - Lisch nodules N.B - very variable expressivity
36
What are lisch nodules?
dome shaped gelatinous masses developing on the surface of the iris. Gold tan-brown colour
37
What other conditions is an individual with neurofibromatosis type 1 at risk of?
- hypertension - scoliosis requiring surgery - pathological tibial fractures - Signficant tumours
38
What tumous are associated with neurofibromatosis type 1?
- phaeochomocytomas - sarcomas - optic pathway gliomas
39
Which gene is involved in neurofibromatosis type 1?
NF1 encoding neurofibromin
40
What is the normal role of neurofibromin?
prevent ras signallying proteins overactivity in the cellular signalling pathway, which promotes cell proliferation
41
What are the chances of offspring being affected if their parent has neurofibromatosis type 1?
- 50% chance of being affected - 100% penetrance - clinical severity is variable
42
What is the inheritance pattern of Duchenne muscular dystrophy?
X-linked recessive inheritance
43
What are the symptoms of Duchenne muscular dystrophy?
``` symptoms usually manifest <5years: - delayed walking - progressive proximal weakness By 7-13: - unable to walk ```
44
What serum changes can be seen in Duchenne muscular dystrophy?
Marked elevation of serum creatinine kinase (from birth as CK leaks out of damaged muscle fibers
45
What are other features of Duchenne muscular dystrophy?
- respiratory failure - cardiomyopathy - scoliosis - non-progressive learning disability
46
What is the average lifespan for someone with Duchenne muscular dystrophy?
25
47
What features can been seen on muscle biopsy from someone with Duchenne muscular dystrophy?
absence of dystrophin protein
48
What is the normal role of dystrophin protein?
crucial in linking the muscle fiber inner structural cytoskeleton (composed of f-actin) to the extracellular matrix proteins (via binding to the dystroglycan proteins)
49
What is the implicated gene in Duchenne muscular dystrophy?
DMD gene encoding dystrophin protein | - mutation usually frame shift
50
What are the features of Becker muscular dystrophy?
- milder - onset ~11years - wheelchair much later if at all - learning disability less common - lifespan may be normal
51
Which gene is implicated in Becker muscular dystrophy?
Caused by same mutation as DMD: - DMD gene encoding dystrophin - mutation usually in frame
52
What is the inheritance pattern of fragile X syndrome?
X-linked recessive with genetic anticipation N.B - can also effect female carriers, with milder learning disability
53
Which gene is implicated in fragile X syndrome?
FMR1 gene encoding FMRP
54
What are the features of fragile X syndrome?
- significant learning diability - enlarged testes after puberty - large ears - long face - prognathism
55
Describe the consequences of a mutation of FMR1
- hypermethylation of FMR1, leading to suppresion of transcription - loss of production of FMRP
56
What is the normal role of FMRP
regulates transcription by binding to mRNA molecules | - though to be necessary for normal learning and memory
57
What is the clinical significance of the repeat tract in the FMR1 gene?
- affected = full mutaion of >200 repeats | - unaffected = ~ 55-200 repeats (premutation)
58
What condition is linked to the FMR1 premutation?
Fragile X associated tremor/ataxia syndrome (FXTAS) - affects 40% males with premutation - 20 % females affected
59
What are the features of Fragile X associated tremor/ataxia syndrome (FXTAS)
- late onset - progressive intention tremor - subsequent cerebellar ataxia
60
Describe the morphological features of Down syndrome
``` Facial features: - upslanting palpebral features - small nose - flat facial profile - epicanthal folds - small, low-set, folded ears Additionally: - single palmar crease - sandal gap ```
61
What are common conditions associated with Down syndrome?
- learning disability - congenital heart defects - hypothyroidism
62
What are the features of trisomy 18?
- small chin - clenched hands with overlapping fingers - malformations of heart, kidney and other organs - if survive past first year - profound learning difficulties
63
What are the features of trisomy 13
- cleft lip palate - abnormal ears - scalp defects - redundant skin around nape - clenched fists - single palmar creases - postaxial polydactyly - cryptorchidism - hypotelorism - micropthalmia - congenital heart defect - normally fatal ~ 1month - profound learning disability N.B - remember baby born @RHF with Patau's!
64
What is hypotelorism?
increased distance between the eyes
65
What is micropthalmia?
abnormally small eyes
66
what is postaxial polydactyly?
Extra digit on little finger side

3. Week 1 - Medical Genetics (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions