Genetics - predisposition to adult onset disease

Question 1

Name some genetically orientated adult onset genetic diseases

Answer 1

Huntington's disease
Osteogenesis imperfecta
Wilson's disease
Polycystic kidney disease
Marfan syndrome
CF
Alzheimer's

Question 2

Mechanisms of adult onset genetic diseases (4)

Answer 2

Single gene
Chromosomal
Mitochondrial
Multifactorial

Question 3

Name some environmentally orientated adult onset genetic diseases

Answer 3

DM
Crohn’s disease
IHD
Ankylosing spondylitis

Question 4

Risk estimation is easier for what mechanism of genetic disorder

Answer 4

Single gene disorders with high penetrance, i.e. autosomal dominant

Question 5

Children or adolescents should only be tested if

Answer 5

there are potential medical benefits

Question 6

Motor neurone disease is generally sporadic or genetic

Answer 6

Sporadic, only 5-10% familial

Question 7

Genes that can cause inherited MND

Answer 7

C9ORF72

SOD1 (superoxide dismutase)

Question 8

SOD1 (superoxide dismutase) is one of the genes that are affected in inherited MND

What is the function of SOD usually

Answer 8

Bind to molecules of copper and zinc to break down toxic, charged oxygen molecules (superoxide radicals)

The superoxide radicals are byproducts of metabolism of cells and must be broken down regularly to avoid damaging cells

Question 9

Does MND have high penetrance?

Answer 9

No, has incomplete penetrance as it can be autosomal dominant or recessive or sporadic

Mutation analysis does not provide certainty

Question 10

Most X-linked conditions are recessive

Which sex is more affected

Answer 10

Males, as they only need one mutated X chromosome to be affected whereas most females are just carriers

Question 11

Cause of Huntington’s disease

Answer 11

CAG repeats

Question 12

Clinical features of Huntington’s disease (7)

Answer 12

Chorea - quick involuntary movements
Athetosis - slower form of chorea
Myoclonus
Rigidity
Cognitive decline
Personality change - irritable
Depression

Question 13

Advantages of predictive testing

Answer 13

Uncertainty of gene status removed
Make plans for future
Arrange surveillance/treatment
Decide whether to have children (if already have then inform their children about it before they have children)

Question 14

Disadvantages of predictive testing

Answer 14

Continued uncertainty about lifespan
Risk of offspring carrying the gene
Impact on self/family