1.4 - Mutations

Question 1

Mutation definition

Answer 1

Mutations are changes in the DNA that can result in no protein or an altered protein being synthesised.

Question 2

Single gene mutations

Answer 2

Single gene mutations involve the altercation of a DNA nucleotide sequence as a result of the substitution, insertion or deletion of a nucleotides.

Question 3

Single gene mutations - substitution

Answer 3

A substitution mutation involves one nucleotide being substituted for another in a DNA sequence.

Question 4

Single gene mutation - insertion

Answer 4

An insertion mutation involves one or more nucleotides being added into a DNA sequence.

Question 5

Single gene mutations - deletion

Answer 5

A deletion mutation involves one or more nucleotides being removed from a DNA sequence.

Question 6

Nucleotide substitutions

Answer 6

Substitution mutations (single gene mutations) affect only one codon.

Types of nucleotide substitutions:

• Missense
• nonsense
• slipce-site

Question 7

Missense mutations

Answer 7

Missense mutations result in one amino acids being changed for another.

This may result in a non-functional protein or have little effect on the protein.

Question 8

Nonsense mutations

Answer 8

Nonsense mutations result in a premature stop codon being produced which results in a shorter protein.

A shortened protein is generally non-functional or its function is affected.

Question 9

Splice-site mutations

Answer 9

Splice-site mutations can result in some introns being retained and/or some exons not being included in the mature transcript.

This may result in a different protein being made.

Question 10

Frame shift mutations

Answer 10

(Nucleotide insertions or deletions result in frame shift mutations).

Frame-shift mutations cause all of the codons and all of the amino acids after the mutations to be changed.

This has a major effect on the structure of the protein being produced. The resulting protein will be significantly altered and is usually non-functional.

Question 11

What is a result of insertion or deletion mutations?

Answer 11

Frame-shift mutations

Question 12

Chromosome structure mutations

Answer 12

Chromosome structure mutations involve change in the number or sequence of genes in a chromosome.

Question 13

Types of chromosome structure mutations

Answer 13

• deletion
• inversion
• duplication
• translocation

The substantial changes in chromosome mutations often make them lethal.

Question 14

Chromosome structure mutations - deletion

Answer 14

Deletion is where a section of a chromosome is removed.

Question 15

Chromosome structure mutations - inversion

Answer 15

Inversion is where a section of a chromosome is reversed.

Question 16

Chromosome structure mutations - duplication

Answer 16

Duplication is where a section of a chromosome is added from its homologous partner.

Question 17

Chromosome structure mutations - translocation

Answer 17

Translocation is where a section of a chromosome is added to a chromosome, not its homologous partner.