DNA testing in diagnosis of neurological disorders Flashcards Preview

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Flashcards in DNA testing in diagnosis of neurological disorders Deck (13):
1

What are unstable repeat expansion?

expansion of a segment of DNA within a specific gene above the threshold - usually consists of repeating units of 3 or more nucleotides eg CAG, CCG

2

what are unstable repeat expansion also called?

dynamic mutations -> size of the expansion is changing

3

Anticipation

the increase in expansion size from generation to generation

4

Huntinton disease is associated with what unstable repeat expansion, what are the effects?

CAG triplet repeat in the coding region of the HTT gene. Leads to toxin protein production Poly -Q HTT -> damages basal ganglia -> atrophy

5

How does Freidrich ataxia occur? when does it usually occur in individuals?

GAA triplet repeat in an intron -> impaired transcription of a Frataxin protein> onset in adolescence (unlike other disorders - mostly late onset)

6

People affected with HD have how many triplet repeats?

>40 CAGs

7

How many CAG repeats is considered normal? how many is normal mutable?

<26 repeats

27-35 = normal mutable (may pass on to offspring)

8

What is the zone of reduced penetrance for HD?

36-39 CAG repeats -> individual may or may not develop the disease

9

Is HD autosomal, X linked? recessive or dominant?

autosomal dominant

10

are the spinocerebellar ataxias autosomal, X linked? recessive or dominant?

Autosomal dominant

11

What triplet repeat is present in the spinocerebellar ataxias and what does it cause?

CAG repeats
mutated protein that affects the functioning of the appropriate ion channel

12

Is Freidrich Ataxia autosomal, X linked? recessive or dominant?

Autosomal recessive

13

How many repeats would an individual with freidrich ataxia have?

66-1700 repeats