Mutations 1.6

Question 1

What are mutations?

Answer 1

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

Question 2

What do single gene mutations involve?

Answer 2

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

Question 3

What are the three types of nucleotide substitutions?

Answer 3

Nucleotide substitutions — missense,
nonsense and splice-site mutations.

Question 4

What is a missense mutation? What may it result in?

Answer 4

Missense mutations result in one amino
acid being changed for another. This may
result in a non-functional protein or have
little effect on the protein.

Question 5

What is a nonsense mutation? What does it result in?

Answer 5

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

Question 6

What does a splice-site mutation result in?

Answer 6

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

Question 7

What do nucleotide insertions or deletions result in?

Answer 7

Nucleotide insertions or deletions result in
frame-shift mutations.

Question 8

What does a frame-shift mutation cause?

What does it have a major effect on?

Answer 8

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

This has a major effect on the structure of the protein
produced.

Question 9

What are the four types of chromosone structure mutations?

Answer 9

Chromosome structure mutations —
duplication, deletion, inversion and
translocation.

Question 10

What is duplication?

Answer 10

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

Question 11

What is deletion (chromosone mutations)?

Answer 11

Deletion is where a section of a
chromosome is removed.

Question 12

What is inversion?

Answer 12

Inversion is where a section of
chromosome is reversed.

Question 13

What is translocation?

Answer 13

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

Question 14

What can substantial changes in chromosone mutations do?

Answer 14

The substantial changes in chromosome
mutations often make them lethal.

Question 15

Why is gene duplication important in evolution?

Answer 15

Duplication allows potential beneficial
mutations to occur in a duplicated gene
whilst the original gene can still be
expressed to produce its protein.