Genetics 2 (Disease Transmission)

Question 1

Whats are the differences between mutations and polymorphisms?

Answer 1

• Mutations: any hereditary changes in genetic material
• Polymorphisms: mutations that occur at >1% frequency in the population

Question 2

What is an example of an autosomal dominant disease and the mechanism of action?

Answer 2

• Huntingdon’s Disease
• HTT gene on Chr 4 codes for huntingtin
• mutation leads to production of toxic protein that accumulates and forms clumps
• causes cell death in basal ganglia of brain
• caused by unstable CAG repeat (more repeats = more likely to get HD)
• severity increases with time
• age of onset decreases

Question 3

What is an example of an autosomal recessive disease and the mechanism of action?

Answer 3

• Cystic Fibrosis
• CFTR gene on Chr 7 codes of cystic fibrosis transmembrane conductance regulator protein
• mutation/lack of functional CFTR gene affects chloride ion function in epithelial cells
• salt/water regulation disruption causes thick mucus

Question 4

What is an example of a mutation in the CFTR gene that’s not cystic fibrosis?

Answer 4

Congenital absence of the vas deferens (CAVD)

Question 5

What is an example of an X-linked recessive condition?

Answer 5

• Haemophilia A and B
• A caused by a mutation in F8 gene on Chr X which encodes factor VIII
• B caused by mutation in F9 gene which encodes factor IX
• B much rarer but symptoms are the same
• treated with clotting factor injections

Question 6

What are the general molecular mechanisms of the different types of genetic disease (autosomal dominant, autosomal recessive, co-dominant)?

Answer 6

• Dominant: toxic product produced (treatment aims to neutralise toxic product)
• Recessive: absence of functional protein (treatment aims to regain function)
• Co-dominant: effects of mutated and normal gene apparent

Question 7

What are the 5 Mendelian inheritance patterns?

Answer 7

• autosomal dominant
• autosomal recessive
• x-linked dominant (rare)
• x-linked recessive
• mitochondrial

Question 8

Why are pedigree diagrams important?

Answer 8

• identifies genetic diseases running in families
• identifies inheritance patterns
• aids diagnosis
• assists in management of condition
• identifies relatives at risk of disease

Question 9

What are the 3 types of heterogeneity, with examples?

Answer 9

• same gene, different mutations, different symptoms: CF and CAVD (CFTR gene)
• same disease, different gene: haemophilia A and B
• same disease, different genes and different inheritance: epidermolysis bullosa

Question 10

What do these symbols show in a pedigree diagram?

Answer 10

males

Question 11

What do these symbols show in a pedigree diagram?

Answer 11

females

Question 12

What do these symbols show in a pedigree diagram?

Answer 12

sex unknown

Question 13

What do these symbols show in a pedigree diagram?

Answer 13

unaffected individual

Question 14

What do these symbols show in a pedigree diagram?

Answer 14

affected individual