DNA Testing: Neurodegenerative Disorders Flashcards

1
Q

What are unstable repeat expansions? what are the most common?

A

Repetitions of >3 nucleotides in tandem

Trinucleotides Repeats

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2
Q

How is it possible for people with fragile X syndrome to develop symptoms when they have a healthy # of repeats?

A

Because the mRNA gains toxic properties

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3
Q

Define: Anticipation

A

Expansion of repeats in the following generations

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4
Q

How is the process of expansion thought to occur?

A

because during replication of the DNA one of the repeats comes off the template strand and other downstream attaches to that site and then normal replication continues to occur

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5
Q

What inheritance pattern shows Huntington’s Disease

A

Autosomal Dominant

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6
Q

Huntington’s Disease age of presentation

A

Adult

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7
Q

at the beggining of the pathology of Huntington’s Disease there is increased movement that progressively disappears T/F

A

T

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8
Q

Where is the repeat found in Huntington’s Disease?
what is the name of the gene?
What does the repeat code for?

A

CAG repeat in exon 1 of the
gene hungtintin in chromosome 4
Poly-glutamine tail (PolyQ)

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9
Q

what cells are affected for the motor changes seen in Huntington’s Disease

A

Medium Spiny Neurons of the basal Ganglia

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10
Q

why is the polyQ tail of the gene problematic if too long

A

can induce apoptosis due to deficient cleaving by caspases that produce N terminals that can aggregate into plaques (more oxidative stress and excitotoxicity)

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11
Q

What are the gene categories found in Huntington’s Disease?

A

Normal (40)

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12
Q

What inheritance pattern shows Spinocerebellar ataxias

A

Autosomal Dominant (late onset)

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13
Q

In Spinocerebellar ataxia SC A6 what is the damaged protein

A

Ca+2 Channel

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14
Q

in SCA6 where is the gene located and how many repeats required to get the condition

A

19

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15
Q

In Fredreich Ataxia what is the inheritance pattern

A

Autosomal Recessive

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16
Q

In Fredreich Ataxia when is the onset

A

puberty

17
Q

Fredreich Ataxia symptoms and signs

A

Progressive limb ataxia, cardiomyopathy, diabetes mellitus

18
Q

In Fredreich Ataxia where is the repeat located

What is the name of the gene? what is its function?

A

In an intron

FXN located in chromosome 9 (ion exchanger in mitochondria)

19
Q

In Fredreich Ataxia how many repeats required for developing symptoms

A

66-1700
Repeats form triple helix that inhibits transcription of the gene (GAA)
Symptoms can also be developed by inactivating point mutations

20
Q

Is genetic testing of children recommended?

A

No as there is nothing to be done

21
Q

Wat is the role of the protein hungtintin?

A

transcription factor for other genes