Autosomal dominant Flashcards

1
Q

Achondroplasia

inheritance

A

autosomal dominant

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2
Q

Achondroplasia

incidence

A

1/15,000-40,000

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3
Q

Achondroplasia

mutation rate?

A

80%

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4
Q

Achondroplasia

penetrance?

A

100%

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5
Q

Achnodroplasia

Clinical manifestations

A

Short
Rhizomelic limb shortening (proximal shortening)
short fingers
genu varum (bow legs)
large head / frontal bossing
midfacial retrusion
small foramen magnum / craniocervical instability

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6
Q

Achondroplasia

Mutated gene?

A

FGFR3

Fibroblast growth factor receptor 3

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7
Q

What does FGFR3 do?

A

Regulates bone growth by limiting the formation of bone from cartilage

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8
Q

FGF43 locus?

A

4p16.3 nucleotide 1138

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9
Q

Achondroplasia mutation?

A

nucleotide 1138 missense
1138G>A
amino acid substitution
Gly380Arg

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10
Q

Achondroplasia mutation consequence

A

Mutation increases the activity of the protein, interfering with skeletal development

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11
Q

What is special about the achondroplasia mutation 1138

A

The 1138 of FGFR3 has the highest known mutation rate in man

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12
Q

Men and de novo autosomal dominant conditions?

A

Men over the age of 40 are noted to have hgiher rate of children with de-novo autosomal dominant conditions - i.e. Achondroplasia

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13
Q

Paternal age effect

A

old dudes yield autosomal dominant mutated sperm

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14
Q

4 syndromes associated with paternal age effect

A

Achondroplasia
Apert syndrome
Crouzon syndrome
Pfeiffer syndrome

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15
Q

Retinoblastoma

what is it?

A

autosomal dominant condition

causes malignant tumor of retina

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16
Q

retinoblastoma incidence

A

1/15,000

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17
Q

retinoblastoma gene?

A

RB1 gene on chromsome 13

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18
Q

Retinoblastoma gene product role?

A

Retinoblastoma associated protein regulates the cell cycle

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19
Q

Retinoblastoma penetrance?

A

90%

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20
Q

Notable clinical finding in retinoblastoma?

A

no reflection of red retina - looks white

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21
Q

Neurofibromatosis Type 1 (NF1)
inheritance
frequency
mutation rate

A

autosomal dominant
1/3000
50% new mutation

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22
Q

NF-1

expressivity?

A

variable

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23
Q

NF-1 Diagnostic criteria

2 or more of the following

A
6 or more cafe au lait
2 or more neurofibromas
1 plexiform neurofibroma
freckling in axillary or inguinal area
optic glioma 
2 or more Lisch nodules
distinctive osseous lesions
affected first degree relative
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24
Q

NF1 mutation?

A

NF1 gene

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25
Q

NF1 gene is what?

A

Neurofibromin - tumor suppressor gene

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26
Q

NF1 locus

A

17q11.2

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27
Q

NF1 type of mutation

A

loss of function

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28
Q

NF1 mutation?

A

over 1000 mutations have been described

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29
Q

What is unique about NF1 and autosomal dominant categorization

A

Must have a mutation in both genes to show phenotype - but inevitably you will get a second random one

30
Q
Tuberous Sclerosis
inheritance?
incidence 
expressivity 
mutation rate?
penetrance?
A

autosomal dominant

1/6000

variable expressivity

1/3 inherited 2/3 de novo

fully penetrant

31
Q

Tuberous sclerosis

skin findings?

A

hypopigmented patches
angiofibroma
shagreen patch
ungual fibroma

32
Q

Tuberous sclerosis

kidneys

A

renal cysts

renal angiomyolipomas

33
Q

Tuberous sclerosis

lungs

A

lymphangioeiomyomatosis

lung muscle cells multiply abnormally

34
Q

Tuberous sclerosis

heart

A

cardiac rhabdomyoma (in infants)

35
Q

Tuberous sclerosis

CNS

A

Subependymal nodules
Subependymal giant cell astrocytomas (SEGAs)
Other cortical dysplasias

Seizures

36
Q

Tuberous sclerosis

Neuropsychiatric

A

cognitive impairment
autism
adhd

37
Q

Tuberous sclerosis
clinical criteria - two major features or one major and 2 minor

Major features

A
angiofibroma
cardiac rhabdomyoma
cortical dysplasia
hypomelanotic macules
Lymphangioleiomyomatosis
multiple retinal nodular harmartomas
renal angiomyolipoma
shagreen patch 
subependymal nodule
SEGA
ungual fibroma
38
Q

Tuberous sclerosis

Minor features

A
confetti skin lesions
dental enamel pits
intraoral fibromas
multiple renal cysts
nonrenal hamartomas
retinal achomic patch
39
Q

Tuberous sclerosis

Mutation?

A

TSC1,

TSC2

40
Q

What do TSC1 and TSC2 do?

A

Encode hamartin and tuberin proteins

41
Q

What do the hamartin and tuerin proteins encoded by TSC1 and TSC2 do?

A

regulate cell growth and proliferation

42
Q

Where are the TSC1 and TSC2 genes effected in tuberous sclerosis located?

A

9 and 16

43
Q

What types of mutations in TSC1 and TSC2 cause tuberous sclerosis?

A

loss of function

44
Q

Osteogenesis Imperfecta type 1
Inheritance?
incidence?
expressivity?

A

autosomal dominant
1/30,000-50,000
variable

45
Q

Osteogenesis imperfecta

Clinical?

A

multiple fractures
mild short stature
adult onset hearing loss
blue sclera

46
Q

Osteogenesis imperfect mutation?

A

COL1A1

Collagen type 1 alpha 1

47
Q

OI mutation = COL1A1

locus?

A

7q21.3

48
Q

OI-typeI
mutated COL1A1
Consequence?

A

Reduced production of pro-alpha 1 chains

Reduces the type 1 collagen production by 1/2

49
Q
Marfan syndrome
inheritance
incidence
mutation rate
expressivity
A

AD

1/5000

25% NEW

Variable

50
Q

Marfan syndrome

clinical

A

Systemic disorder of connective tissue
ocular
skeletal
cardiovascular

51
Q

Marfan diagnosis

no family history

A
aortic root enlargement 
plus one...
ectopia lentis
FBN1 mutation 
systemic score>7
52
Q

Marfan diagnosis

family history

A

any…
ectopia lentis
systemic score >7
aortic root enlargement

53
Q

Most notable clinical manifestations of Marfan’s

A
Aortic root enlargement
Scoliosis 
Ectopia lentis
Thumb and wrist sign
Pectus excavatum
54
Q

Marfan mutation in?

A

FBN1

Firbillin-extracellular matrix protein

55
Q

FBN1

Locus?

A

15q21.1

56
Q

Marfan mutation type?

A

Dominant negative

57
Q

Marfan mutation consequence

A

severe reduction in the number of microfibrils

58
Q

Trinucleotide repeat disorders

A

Expansion of segment of DNA consisting of three or more nucleotides

Slipped mispairing

Anticipation

Parental Transmission Bias

59
Q

Trinucleotide repeat

mode of inheritance?

A

AD,
AR
X linked

60
Q

Slipped mispairing

A

Mispairing of bases in regions of repetitive DNA replication couple with inadequate DNA repair

As the repeat grows longer, the probability of subsequent mispairing increases

In germ cells

61
Q

Huntington Disease
inheritance
incidence

A

Autosomal dominant

1/10,000

62
Q

Huntington disease

Parental bias

A

Early onset - paternal

later onset - maternal

63
Q

Huntington disease

Clinical

A

Progressive neuronal degeneration causing motor, cognitive, and psychiatric disturbances

64
Q

Huntington

age of onse

A

35-44

65
Q

Huntington death?

A

15 yr post onset

66
Q

Huntington

Mutation

A
HTT
Huntingtin
Cromosome 4p16.3
The expansion of glutmaine may cause an altered structure or biochemical protein property 
CAG
67
Q

CAG Repeat threshold?

A

> 39 full penetrance

>60 juvenile onset

68
Q

Myotonic dystrophy type 1
repeat?
incidence
parental bias?

A

CTG
1/20,000
Maternal

69
Q

Myotonic dystrophy 1

Clinical

A
Adult onset muscular dystrophy
Progressive muscle wasting and weakness
myotonia
cataracts
cardiac conduction defects
70
Q

Myotonic dystrophy mutation?

A

DMPK
Myotonic dystrophy protein kinase
19q13.3
plays important role in muscle heart and brain

71
Q

Myotonic dystrophy

CTG threshold?

A

5-34 normal
34-49 premutation
>50 full mutation with 100% penetrance