Lecture 2

Question 1

What are the two main causes of mutations?

Answer 1

Endogenous mutations and mutagens

Question 2

What is an endogenous mutation?

Answer 2

A mutation which is caused due to spontaneous errors in DNA replication and repair

Question 3

What is a mutagen?

Answer 3

A chemical that enduces damage to damage to DNA causing mutations to occur

Question 4

What are the three types disorders that can arise from mutations?

Answer 4

Single gene disorders
Chromosome disorders
Complex/multi factorial disorders

Question 5

What are the 6 types of chromosomal mutations?

Answer 5

Translocations,
Deletions,
Inversions,
Chromosome loss
Chromosome duplication

Question 6

What are the two classes of substitution mutations?

Answer 6

Transition mutations and transversion mutations

Question 7

What is a transition mutation?

Answer 7

When a purine is exchanged for another purine (A with G), or a pyrimidine is exchanged with another pyrimidine (C with T)

Question 8

What is a transversion substitute mutation?

Answer 8

When a purine is replaced by a pyrimidine or vice versa (A to C) or (G to T) etc

Question 9

What is the hotspot that differs from theoretical predictions of transversions being more common?

Answer 9

A c to T mutation

Question 10

What ate the three effect based classifications of substitution mutations?

Answer 10

Silent mutations,
Nonsense mutations,
Missense mutations

Question 11

What is premature protein truncation?

Answer 11

When the effect of a mutation results in a stop codon appearing earlier than it should resulting a shortened protein that may or may not be functional

Question 12

What are the two types of Missense mutations?

Answer 12

Conservative where a similar type of amino acid is replaced resulting in little effect on function
Non-conservative where the amino acid replaced is dissimilar so a serious effect on function can occur

Question 13

Where are the three regions where pathogenic mutations occur?

Answer 13

The coding region
Areas affecting gene regulation
Mutations affecting RNA stability of splicing

Question 14

What is a frame shift mutation?

Answer 14

When an insertion or deletion of a base pair results in a change in the reading frame usually causing premature truncation and severe deleterious effects

Question 15

What are the three factors that affect the phenotype seen from a premature truncation?

Answer 15

The stability of the polypeptide product
The extent of truncation
The functional importance of the missing amino acids

Question 16

What are the inheritance features of an autosomal recessive disease?

Answer 16

The carriers are asymptomatic, typically not seen in parents, males and females equally affected
Risk 1:4

Question 17

What are the inheritance features of an Autosomal Dominant Disease?

Answer 17

Phenotype typically appears in every generation, Risk 1:2 at least one paretn will display the phenotype

Question 18

What are the inheritance features of a recessive x-linked disease?

Answer 18

Sons only inherit this from the mother, A male will pass on condition to all daughters, the incidence of disease is much higher in males
Disease is milder in women due to random X inactivation

Question 19

What are the inheritance features of a dominant x-linked disease?

Answer 19

Male parents have no affected sons but all daughters affected
Females typically have a less severe disease
More common for females to have the disease

Question 20

What are the inheritance features of a Y linked dominant disease?

Answer 20

Disease can only pass from male to male
Only males are affected
All sons of affected male are affected