Huntington disease

Question 1

_____, a cause of progressive chorea and dementia, is inherited as an autosomal dominant trait and is caused by an unstable length mutation in the ____.

Answer 1

Huntington’s disease; huntingtin (HTT ) gene

Question 2

Normally, ____ adjacent copies of a CAG repeat are found in the first exon, within the coding sequence, whereas in patients affected with Huntington’s disease the repeat tract is expanded to ____.

Answer 2

10 – 35 (most commonly 15 – 20, with a median of 18); 36 – 120 copies (commonly 40 – 55)

Question 3

At the other end of the spectrum, patients w/ the ____form of Huntington’s disease tend to show the largest expansions, usually more than ____ repeats, but a wide range of age of onset is observed for any specific repeat number

Answer 3

juvenile form; usually more than 60 CAG repeat units

Question 3

Incomplete penetrance of Huntington disease is associated w/ repeat tracts in the ____.

Answer 3

36 – 39 range.

Question 4

T/F. The repeat size associated with Huntington disease is generally stable at maternal transmission but tends to increase at paternal transmission.

Answer 4

True.

Question 5

Presymptomatic carrier detection & prenatal diagnosis can be offered by direct ____.

Answer 5

DNA analysis

Question 6

The precise mechanism of pathogenesis of the expanded polyglutamine tract is under investigation but may involve the production of _____, due to hydrogen bonding between the expanded polyglutamine stretches of neighbouring HTT protein molecules, or the generation of _____.

Answer 6

toxic insoluble aggregates of HTT protein; toxic proteolytic fragments of the mutant HTT