genetic predisposition of adult onset disease

Question 1

what is penetrance?

Answer 1

this is a measurement of how many people with a particular genotype display that phenotype.

For example - Huntingtons disease has a 100% penetrance (meaning anyone with the gene will inevitable develop the disease).

Question 2

what is predictive testing?

Answer 2

Testing someone currently well to predict their future.

Question 3

what is carrier testing?

Answer 3

testing done to determine if someone is a carrier of an autosomal recessive gene.

Question 4

what is cascade screening?

Answer 4

screening of family members to identify if they are at risk of a hereditary disease.

Question 5

how can genetics be altered?

4 methods

Answer 5

• Single gene: (x-linked), autosomal dominant, autosomal recessive.
• chromosomal: trisomy
• Mitochondrial
• Multifactorial

Question 5

how can genetics be altered?

4 methods

Answer 5

• Single gene: (x-linked), autosomal dominant, autosomal recessive.
• chromosomal: trisomy
• Mitochondrial
• Multifactorial

Question 6

what are characteristics of an entirely genetic disease?

Answer 6

• unifactorial
• rare
• high recurrence rate for family members

Question 7

what are characteristics of a more environmental disease?

Answer 7

• common
• genetic complex
• multifactorial
• low recurrence rate

Question 8

what must genetic test information be able to do?

Answer 8

• benefit the patient

- allow for prevention or treatment

Question 9

what is x linked inheritance?

Answer 9

when the gene causing the disease is located on the X chromosome.

Question 9

what is x linked inheritance?

Answer 9

when the gene causing the disease is located on the X chromosome.

Question 10

what is a non-penetrant individual?

Answer 10

when someone has the genotype for a disease but it fails to cause disease.

Eg - women with BRCA1 who never develop breast cancer.

Question 11

What is ALS?

Answer 11

amyotrophic lateral sclerosis (motor neurone disease)

Question 12

how much motor neurone disease is genetic?

Answer 12

5-10%, the rest is sporadic.

There is no PARTICULAR gene which causes ALS.

Question 13

what type of autosomal gene can ALS be?

Answer 13

The gene causing motor neurone disease can be either autosomal dominant OR recessive.

Question 13

what type of autosomal gene can ALS be?

Answer 13

The gene causing motor neurone disease can be either autosomal dominant OR recessive.

Question 14

what is the average onset of MND?

Answer 14

55yrs.

But YOUNGER in familial forms.

Question 15

what are the most common types of motor neurone disease?

Answer 15

amyotrophic lateral sclerosis

progressive bulbar palsy

Question 16

what is the most common cause of death in MND?

Answer 16

respiratory failute

Question 17

what enzyme is affected in ALS?

Answer 17

SOD
superoxide dismutase

(20% in familial cases, only 2% in non familial cases).

Question 18

what is the role of SOD?

Answer 18

This is an enzyme which breaks down harmful oxygen molecules (free radicals) preventing tissue damage.

Question 19

what is the treatment for ALS?

Answer 19

No cure or good treatment.

Question 20

what is Huntingtons disease?

Answer 20

An adult onset autosomal dominant disease.

Question 21

what are the clinical features of Huntingtons disease?

Answer 21

Chorea
athetosis (slow writhing movements)
myoclonis
rigidity
poor planning
un classical dementia
irritable
depressed
anxious
loss of empathy
paranoia 
psychosis
disinhibition
Wide stance

Question 22

what is the onset for Huntingtons disease?

Answer 22

early 30s or 40s.

Question 23

what is the life expectancy for Huntingtons disease?

Answer 23

15-20 years from ONSET of disease.

Question 24

what is the treatment for Huntingtons disease?

Answer 24

no satisfactory treatment.

Question 25

How penetrant is Huntingtons disease?

Answer 25

100%.

Question 26

what happens to children who develop Huntingtons disease from their patient?

Answer 26

It usually is worse and has a younger onset (ANTICIPATION).

Question 27

what gene and chromosome is effected in Huntingtons disease?

Answer 27

Gene HTT on chromosome 4.

Question 28

what is the most common cause of death from Huntingtons disease?

Answer 28

Pneumonia (often aspiration)

suicide

Question 29

which parts of the brain are targeted in Huntingtons disease?

Answer 29

the caudate and putamen.

Question 30

what type of disorder is Huntingtons disease?

Answer 30

A triple repeat disorder.

Question 31

what is anticipation?

Answer 31

When there is more genetic multiplication in offspring.

So a disease becomes more serious and has an earlier onset as it travels down through offspring.