X linked and mitochondrial inheritance Flashcards

1
Q

X chromosome inactivation occurs when?

A

1st week of embryogenesis

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2
Q

Nonrandom vs skewed x chromosome inactivation

A

Nonrandom- when structurally abnormal x chromosome present, more of normal xs are turned on usually
Skewed- observed when female shows signs of x linked recessive condition

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3
Q

X linked dominant conditions (4)

A

Hypophosphatemic Rickets
Fragile X syndrome
Charcot Marie Tooth
Rett Syndrome

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4
Q

Clinical manifestation of hypophosphatemic rickets (3)

A

Hypophosphatemia
short stature
bone deformity

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5
Q

Mutation leading to hypophosphatemic rickets occurs on the ____ gene which regulates _____. This inhibits ______

A

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

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6
Q

Fragile X syndrome gene

A

FMR1

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7
Q

Fragile X syndrome exhibits ______ and ________.

A

Anticipation

Maternal transmission bias

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8
Q

Clinical manifestations of Fragile X (6)

A
intellectual disabilities
large ears, long face, macroorchidism
autistic behavior
social anxiety
hand flapping/biting
agression
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9
Q

Other conditions associated with FMR1

A

Fragile X Associated Tremor Ataxia (FXTAS)

FMR1- related primary ovarian insufficiency

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10
Q

CGG repeats fragile X: grey zone, premutation, and full mutation

A

46-65: Grey
56-200: Premutation
>200: Full mutation

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11
Q

Mutation rate of Rett syndrome

A

95%

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12
Q

Clinical Manifestations of Rett syndrome (6)

A
Loss of normal movement and coordination 
Acquired microcephaly
Loss of communication skills
Failure to thrive
Seizures
Abnormal hand movements
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13
Q

Rett syndrome gene mutation

A

MECP2

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14
Q

MECP2 gene (Rett) encodes for what protein?

A

Methyl CpG binding protein

Essential for the normal function of nerve cells

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15
Q

X-linked Recessive Disorders (4)

A

Lesch-Nyhan Syndrome
Hemophilia A
Fabry’s disease
Dystrophonpathies

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16
Q

Clinical Manifestations of Lesch-Nyhan (4)

A

Cerebral palsy
Cognitive and behavioral disturbances
Overproduction of uric acid
Self injury

17
Q

Gene mutation Lesch Nyhan

A

HPRT1
Hypoxthine phosphoribosyltransferase
recycling of purines

18
Q

Gene mutation for Duchenne and Becker Muscular dystrophies

A

DMD

encoding for dystrophin

19
Q

Location of DMD on chromosome

A

Xp21-21.1

20
Q

Clinical Manifestations of Duchenne (8)

A
Progressive muscular weakness proximal > distal
Calf hypertrophy
Dilated cardiomyopathy
CK levels 10x normal
Onset before the age of 5
Wheelchair bound before 13
Death in their 30’s
Absence of Dystrophin
21
Q

Clinical manifestations of Becker (7)

A

Progressive muscular weakness proximal > distal
Dilated cardiomyopathy
CK levels 5x normal
Later onset
Wheelchair bound after 16
Death in their 40’s
Abnormal quantity or quality of Dystrophin

22
Q

DMD-associated DCM

A

Dilated cardiomyopathy presenting between 20-40 years of age
Early death
No skeletal muscle involvement
No Dystrophin in the myocardium

23
Q

What percentage of Hemophilia A carrier females are affected?

A

10%

24
Q

Clinical manifestations of Hemophilia A

A

Blood disorder where blood fails to clot appropriately due to a deficiency of Factor VIII
Spontaneous bleeds into joints, muscles or intracranial
Excessive bruising
Prolonged bleeding after injury or incision
Delayed wound healing

25
Q

Gene mutation of Hemophilia A

A

F8

Encoding for Factor VIII

26
Q

Chromosome location for Hemophilia A mutation

A

Xq28

22A inversion causes 50%

27
Q

How many genes does mtDNA encode?

A

37

28
Q

Mitochondrial DNA mutation diseases (4)

A

Kearnes-Sayre
MELAS
MERFF
Leber Hereditary Optic Neuropathy

29
Q

Clinical manifestations of Kearnes-Sayre (7)

A
Triad:
Pigmentary Retinopathy
Progressive External Ophthalmoplegia
And onset before age 20y
Cardiac conduction defects
Ataxia
Deafness
Kidney problems
30
Q

MELAS and MERFF have a high or low new mutation?

A

Low

31
Q

Clinical manifestations of MELAS (5)

A
Starts between age 2 & 10 y
Muscle weakness 
Seizures
Repetitive stroke-like episodes
Elevated lactic acidosis
32
Q

Most common gene mutation in MELAS

A

MT-TL1 (80%)

33
Q

MERRF clinical manifestations (5)

A
Muscle symptoms
Seizures
Ataxia
Dementia
Ragged-red fibers
34
Q

Gene mutation for MERFF

A

MT-TK

35
Q

Clinical manifestations of Leber hereditary Optic Neuropathy

A

Bilateral subacute vision failure

Occurs during young adulthood