Lecture 17 Flashcards

1
Q

mitochondrial inheritance as seen on a pedigree?

A
  1. all offspring of affected female are affected
  2. only females transmit the disease
  3. can occur in both genders
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2
Q

Explain heteroplasmy?

A

The severity of the disorder depends on the number of mitochondria that have the mutant gene

explains variable expression

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3
Q

Examples of mitochondrial diseases

A
  1. Leber hereditary optic neuropathy
  2. MELAS
  3. MERRF
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4
Q

example of a digenic disorder?

A

Retinitis pigmentosa

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5
Q

Imprinting disorders

A

Prader Willi syndrome

Angelman syndrome

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6
Q

Triplet repeat disorders

A
Huntington disease (autosomal dominant) 
Myotonic dystrophy (autosomal dominant)
Fragile X syndrome (X-linked)
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7
Q

How do digenic disorders occur?

A

Mutations in two genes (A, B) are additive and necessary to produce the disorder

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8
Q

retinitis pigmentosa

A

digenic disorder

progressive visual impairment
a result of a mutation in two independent genetic loci (ROM1 and peripherin)
Heterozygotes for gene A and gene B have retinitis pigmentosa

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9
Q

Prader- willi syndrome

A

microdeletion of paternal chromosome 15

microdeletion of the paternal SNRPN gene

no active copy of the SNRPN gene (maternal copy is silenced)..but has two active copies of the UBE3A gene

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10
Q

symptoms of prader-willi syndrome

A

Children are usually obese, have mental and developmental delay and underdeveloped genitalia

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11
Q

how can methylated DNA be analyzed?

A

southern blot

PCR and DNA sequencing

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12
Q

angelman syndrome

A

deletion of the maternal gene UBE3A

two copies of the SNRPN gene and no UBE3A gene functioning

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13
Q

symptoms of angelman syndrome

A

Severe intellectual disability
seizures
Puppet like posture of limbs

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14
Q

What basepairs are repeated in fragile X syndrome

A

CGG

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15
Q

What basepairs are repeated in Friedrich ataxia

A

GAA

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16
Q

What basepairs are repeated in HD

A

CAG

17
Q

What basepairs are repeated in Myotonic

dystrophy

A

CTG

18
Q

What is anticipation?

A

The larger the repeat, the greater is the chance for it to be unstable and it tends to expand from one generation to the next

19
Q

What diseases are anticipation found?

A
  1. HD
  2. myotonic dystrophy
  3. Fragile X syndrome
20
Q

What gene mutation leads to fragile X syndrome

A

FMR1

21
Q

symptoms of fragile X syndrome

A
Intellectual disability
learning difficulties
prominent ears
elongated face
macro orchidism

females are less impacted
shows anticipation
more repeats = increased severity

22
Q

Fragile X syndrome diagnostic test

A

southern blot analysis