2 - Risk of transmission of disease

Question 1

What are the types of genetic disease?

Give an example of each

Answer 1

monogenic e.g. Huntington’s, CF, Haemophilia

complex disorders e.g. Type 2 diabetes, schizophrenia, Crohn’s disease

Question 2

What are point mutations?

Answer 2

a single change in the DNA sequence

Question 3

What are the 2 types of point mutations?

Answer 3

missense and nonsense

Question 4

What are missense mutations?

Answer 4

mutations that result in a different amino acid being coded for

Question 5

What are nonsense mutations?

Answer 5

mutations that result in the STOP codon, so the polypeptide chain ends prematurely

Question 6

What are the 2 types of frameshift mutations?

Answer 6

insertions and deletions

sometimes referred to as InDel

Question 7

When drawing pedigrees, what is the symbol if the sex is unknown?

Answer 7

a diamond

Question 8

How are the deceased represented on pedigree diagrams?

Answer 8

diagonal line through square/circle/diamond

Question 9

How are pregnant people represented on pedigree diagrams?

Answer 9

a P in the centre of the shape

Question 10

On pedigree diagrams, how is the person providing the information highlighted?

Answer 10

with an arrow towards the bottom the the shape

Question 11

Who is affected by X-linked recessive conditions?
Who is a carrier of these conditions?
Give an example of an X-linked recessive condition?

Answer 11

usually only males
females
e.g. haemophilia

Question 12

How can haemophilia be treated?

Answer 12

with injections of clotting factor

Question 13

What are the similarities and differences between haemophilia A and B in terms of symptoms?

Answer 13

symptoms are identical in both

haemophilia B is much rarer

Question 14

Genetic heterogeneity:
give an examples of 2 diseases with
the same gene
different mutation
different symptoms

Answer 14

Cystic fibrosis and CAVD

Question 15

Genetic heterogeneity:
give an examples of 2 diseases with
the same disease
different genes

Answer 15

Haemophilia A and B

Question 16

Genetic heterogeneity:
give an examples of 2 diseases with
the same disease
different genes
different inheritance patterns

Answer 16

different forms of epidermolysis bullosa

Question 17

Define pentrance

Answer 17

the proportion of individuals with the disease-causing mutations (the genotype) that also express the associated symptoms (the phenotype)

Question 18

Define (variable) expressivity

Answer 18

disease severity may vary between individuals with the same disease-causing mutation

Question 19

Define phencopy

Answer 19

having the same disease, but with a different underlying cause
e.g. obesity

Question 20

Define epistasis

Answer 20

interactions between disease gene mutations and other modifier genes can affect the phenotype
e.g. severity of CF
a type of gene action where one gene can suppress the action of another (nonallelic) gene