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M2M2 > X-linked > Flashcards

X-linked Flashcards

1
Q

Mechanism of X chromosome inactivation -

A

XIST gene located on the X chromosome

expressed only from the inactive X

required for X inactivation

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2
Q

Hypophasphatemic rickets
inheritance
incidence

A

X-linked dominant

1/20,000

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3
Q

Hypophosphatemic rickets

clinical

A

low phosphate in blood
short stature
bone deformity

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4
Q

Hypophosphatemic rickets

mutation?

A

PHEX
Regulates fibroblast growth factor
Inhibits kidneys ability to reabsorb phosphate into the blood stream

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5
Q

Fragile X
inheritance
mutation?

A

X linked dominant

FMR1

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6
Q

Fragile X

mutation issue?

A

trinculeotide repeat

CGG

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7
Q

Fragile X
incidence
m and f

A

m
1/2500-4000
f
1/7000-8000

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8
Q

What is the most common caused of inherited developmental delay?

A

fragile x

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9
Q

Since fragile x is a trinucleotide repeat, what do we see?

A

anticipation

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10
Q

fragile x

parental bias

A

mom

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11
Q

fragile x

clinical

A 
intellectual
dysmophic: large ears, long face, macroorchidism
autistic
anxiety 
hand flapping biting 
aggression
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12
Q

fragile x premutation FMR1 associated conditions?

A

Fragile x associated tremor ataxia FXTAS - white matter lesion on MRI / intention tremor / gait ataxia

FMR1 -related primary ovarian insufficiency - menopause

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13
Q

fragile x CGG thresholds

A

6-45 normal
46-55 grey
56-200 Premutation (FXTAS/POI)
>200 full mutation

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14
Q

Rett Syndrome
inheritance?
incidence
new mutation?

A

X linked dominant
1/10,000
95%

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15
Q

Rett

clinical?

A 
loss of normal coordination
acquired microcephaly
loss of communication
failure to thrive
seizures
abnormal hand movement
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16
Q

Rett

mutation?

A

MECP2
MethyL CpG binding protein
Essential for normal function of nerve cells

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17
Q

Lesch Nyhan
inheritance
incidence

A

X linked recessive

1/380,000

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18
Q

Lesch Nyhan

Clinical?

A

cerebral palsy
cognitive/behavior
overproduction uric acid
self injury

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19
Q

Lesch Nyhan mutation?

A

HPRT1
Hypoxanthine phosphoribosyltransferase 1
Recycling of purines

20
Q

Dytrophinopathies
inheritance
what are they
3 examples

A

x-linked recessive
spectrum of muscle diseases from mild to severe

Becker MD
Duchenne MD
DMD associated dilated cardiomyopathy

21
Q

Dystrophinopathies
Mutation?
Loci?

A

DMD
Xp21-21.1
dystrophin

22
Q

What is the largest human gene?

A

dystrophin

23
Q

Duchenne

Clinical

A 
progressive muscle weakness from proximal to distal
calf hypertrophy
dilated cardiomyopathy
CK level 10x normal
onset before 5
wheelchair bound before 13
death in 30s 
absence of dystrophin
24
Q

Becker

Clinical

A 
Progressive muscle weakness proximal > distal
dilated cardiomyopathy
CK levels 5x normal
later onset
wheelchair bound after 16
death in 40s
abnormal quality dystrophin
25
Q

DMD associated DCM

Clinical

A

dilated cardiomyopathy presenting between 20-40
early death
no skeletal muscle involvement
no dystrophin in myocardium

26
Q

Hemophilia A
inheritance
incidence
carrier females affected?

A

x linked recessive
1/4000 male births
10% carrier females affected

27
Q

Hemophilia A

clinical

A

blood disorder where blood fails to clot due to deficient factor VIII
Spontaneous bleeds into joints, muscles, or intracranial
excessive bruising
prolonged bleeding
delayed wound healing
royal family

28
Q

Hemophilia A

gene mutated?

A

F8
Xq28
Deficient factor VIII

29
Q

50% hemophila A is due to?

A

22A inversion

30
Q 
Mitochondrial DNA 
#genes
A

37

31
Q

Characteristics of mtDNA (4)

A

maternal inheritance
replicative segregation
homoplasmy/heteroplasmy
threshold effect

32
Q

mtDNA

Replicative segregation

A

At cell division the multiple copies of mtDNA replicate and sort randomly among newly synthesized mitochondria

this could be normal or mutated DNA

33
Q

Heteroplasmy

A

Cells have both mutant and normal mitochondria / threshold for if phenotypic consequence

34
Q

mitochondrial disease tends to affect tissues that?

A 
Rely on oxidative phosphorylation
brain
retina
skeletal muscle
heart
35
Q

mitochondrial diseases (4)

A

Kearns-Sayre syndrome
MELAS
MERRF
Leber Hereditary Optic Neuropathy

36
Q

Kearns Sayre Syndrome

incidence

A

mtDNA - large deleation (usually removes 12 genes)
1-3/100,000
Most commonly caused by somatic mutation

37
Q

Kearns Sayre

clinical

A

triad

  • pigmentary retinopathy
  • progessive external ophthalmoplegia
  • onset before 20

cardiac conduction defects
ataxia
deafness
kidney problems

38
Q

MELAS
Mitochondrial encephalomyopathy, lactic acidosis and stroke like episodes

inheritance
incidence
new mutation?

A

mitochondrial

1/300,000

low new mutation

39
Q

MELAS

clinical

A 
2-10y/o
muscle weakness
seizures
repetetive stroke like episodes
elevated lactic acidosis
40
Q

MELAS Mutations?

A

Mitochondrial genes

MT - ND1/ND5/TH/TL1 (80%) /TV)

41
Q

MERRF

Myocloinic epilepsy with ragged red fibers

A

mt
1/400,000
low new mutation

42
Q

MERRF

CLINICAL

A 
muscle symptoms
seizures
ataxia
dementia
ragged red fibers
43
Q

MERRF

Mutation?

A

mitochondrial genes

MT-TK

44
Q

Leber Hereditary Optic Neuropathy

A

mt

1/30-50,000 europeans

45
Q

Leber Hereditary Optic Neuropathy

A

bilateral subacute vision failure

occurs during young adulthood

46
Q

Leber Hereditary Optic Neuropathy

Mutation?

A

mt DNA

point mutations

M2M2 (27 decks)

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