Genetics Flashcards
What type of genetic disorder is Huntington’s?
Autosomal dominant
What does the Huntington gene code for?
Huntington protein
What is the Huntington protein formed by?
Expansion of the CAG triplet repeat
What is CAG the code for?
The amino acid glutamine
What do more CAG repeats cause?
A longer chain of glutamines in the protein, which cause the huntingtin protein to be misshapen.
This causes gradual damage to brain cells, although the exact mechanism through which this occurs is not known.
Huntington’s disease exhibits __________
ANTICIPATION
What is anticipation?
Where the disease has an earlier age of onset in each generation
What signs/symptoms can be the first indicator or Huntington’s disease?
Depression and/or anxiety
List psychiatric symptoms which a person with Huntington’s Disease may develop.
- Depression
- Anxiety
- Compulsions
- Psychosis
- Suicidality
- Aggression
- Blunted affect
What is blunted affect?
Reduced/lack of emotional response
What are compulsions?
E.G gambling or addictions
What can suicidality be related to?
Either other mental health symptoms, or to the knowledge of the symptoms they will develop (or both).
Give examples of 3 cognitive symptoms that may arise in Huntington’s.
- Decline in executive function
- Short and long-term memory deficits
- Dementia
What does executive function refer to?
Planning, abstract thinking, cognitive flexibility
What is dementia defined as?
Progressive decline in global cognition
List motor problems which may potentially arise in Huntington’s.
- Choreiform movements
- Rigidity
- Gait disturbance
- All actions involving muscle control become impaired
- Problems chewing, swallowing, speaking
- Writhing movements
What are choreiform movements?
Brief, irregular, non-repetitive movements
What chromosome is the CAG repeat encoding poly-glutamine?
4
What is the most common form of dementia?
Alzheimers
Outline 3 main changes that occur in the brain of someone with dementia.
- Extreme shrinkage of the hippocampus
- Extreme shrinkage of the cerebral cortex
- Severely enlarged ventricles
What are the prominent symptoms of Alzheimers?
Short term memory dysfunction – learning new things is difficult, BUT remembering things that happened a long time ago (episodic memory), facts learned a long time ago (semantic memory) and carrying out tasks already well practised (implicit memory) are not as affected.
List 4 other very common symptoms of Alzheimers.
- Dysphasia
- Dyspraxia
- Agnosia
- Mood symptoms
What happens in end stage disease of Alzheimers?
People are bed bound, fully dependent and lose the ability to swallow
TERMINAL illness
What is the average life expectancy after diagnosis of Alzheimers?
7 years
What does Alzheimers (pathologically) involve the formation of?
Extracellular amyloid plaques
What do extracellular amyloid plaques cause?
Inflammation, and neurofibrillary tangles inside the cells
What causes the formation of neurofibrillary tangles?
Tau protein involved in the microtubules is hyperphosphorylated, and causes the tangles
What is the lifetime risk of developing Alzheimers?
10%
If a person has one affected first degree relative, what is the risk of developing Alzheimer’s?
25%
What % does early onset familial disease account for?
2%
Recurrence in dizygotic twins of bipolar %?
14%
Recurrence in monozygotic twins in bipolar %?
57%
What type of testing do monogenetic disorders get?
Presymptomatic testing
