Session 13-Intro To Mutations

Question 1

What is a mutation?

Answer 1

Heritable alteration in a gene or chromosome (change in sequence of nucleotides) but also the process that produces the alteration

Question 2

What are the exogenous ways that can lead to mutations? (2)

Answer 2

Ionising radiation/particles and free radicals

Mutagenic chemicals and anti-cancer agents

Question 3

What are the endogenous ways that can lead to a mutation? (2)

Answer 3

DNA replication defects

Transposable elements

Question 4

What are transposable elements?

Answer 4

They don’t have a fixed position in the genome; they can move to random sites from one chromosome to another

Question 5

True or false: small genes are easily disrupted by transposable elements

Answer 5

FALSE - large genes are more easily disrupted eg. BRCA1 gene for breast cancer

Question 6

What are transition changes?

Answer 6

Change to the same type of base:
Purine to purine
Pyrimidine to pyrimidine

Question 7

What are transversion changes?

Answer 7

Changes to different type of base:

Purine to pyrimidine or vice versa

Question 8

Where is the mutation for sickle cell anaemia and what type of mutation is it?

Answer 8

Codon 7 of HBB
Base substitution mutation (missense)
One AA change (6th AA) Glu -> Val

Question 9

Define missense

Answer 9

Changing one AA to another AA, mutations that change gene products

Question 10

Which type of mutations do not have an effect? (2)

Answer 10

Silent or neutral mutations 
Synonymous mutations (both codons code for same AA)

Question 11

What type of mutations change the polypeptide length? (3)

Answer 11

1. Frameshift - insertions or deletions
2. Mutations of a stop codon
3. Nonsense mutations - stop codon is created

Question 12

What type of mutations change the amount of gene product? (2)

Answer 12

Mutations affecting transcription

Mutations affecting translation