WEEK 14 (Mutations caused by expandable DNA repeats)

Question 1

What are Trinucleotide repeat sequences?

Answer 1

Specific short DNA sequences repeated many times

Question 2

Describe Fragile X Syndrome

Answer 2

An X-linked dominant inherited disorder which is caused by CGG trinucleotide repeats in FMR1 gene

SYMPTOMS:
- Severe intellectual disability
- Large prominent ears
- Large testes
- Elongated face (Large chin)

Question 3

Describe Myotonic Dystrophy

Answer 3

An autosomal dominant disorder which is caused by a CTG trinucleotide repeat expansion in the DMPK gene which leads to an abnormal expression of MYOTONIN PROTEIN KINASE leading to MYOTONIA

SYMPTOMS:
- Muscle wasting
- Cataracts
- Frontal balding
- Gonadal atrophy (shrinkage of testes)
- Arrhythmia

Question 4

An increased number of trinucleotide repeats will cause what?

Answer 4

A more severe form of the disease and an earlier onset of the disease

Question 5

What is the most common genetic cause of intellectual disability?

Answer 5

Down syndrome

Question 6

What is the most common inherited cause of intellectual disability?

Answer 6

Fragile-X Syndrome

Question 7

Describe Huntington Disease

Answer 7

An autosomal dominant trinucleotide disorder caused by CAG trinucleotide repeat expansion in the Huntington gene on chromosome 4; symptoms manifest between ages 20 and 50

SYMPTOMS:
- increased dopamine, decreased GABA & Acetylcholine in brain
- Aggression
- Depression
- Dementia

Question 8

Define Anticipation

Answer 8

Increased severity or earlier onset of disease in succeeding generations