Key Area 6: Mutations

Question 1

What are mutations?

Answer 1

Changes in the DNA that can result in no protein or an altered protein being synthesised.

Question 2

What are some characteristics of mutations?

Answer 2

They are normally rare, spontaneous, and rendom and most are harmful or lethal.

Question 3

What is a single gene mutation?

Answer 3

Changes in the type, order, or number of nuclotides within a gene, causing an alteration in the resulting protein.

Question 4

What can cause single gene mutations?

Answer 4

Substitution, Insertion, or deletion of nucleotides.

Question 5

What are altered proteins often described as?

Answer 5

Non-functioning

Question 6

What is a single gene substitution mutation?

Answer 6

One DNA nucleotide is swapped/substituted for another.

Question 7

What are 3 examples of single gene substitution mutations?

Answer 7

Missense, nonsense and splice-site mutations.

Question 8

What is a missense mutation?

Answer 8

When one amino acid is changed for another.

Question 9

What can missense mutations result in?

Answer 9

They can either have little effect, or result in a new, non-functional protein being produced.

Question 10

What is a nonsense mutation?

Answer 10

Where a premature stop codon is produced.

Question 11

What are the effects of a nonsense mutation?

Answer 11

A shorter protein is produced.

Question 12

What is a splice-site mutation?

Answer 12

Where some introns are retained and/or some exons are not included in the mature mRNA transcript.

Question 13

What is an single gene inversion mutation?

Answer 13

They involve an extra DNA nucleotide being added or inserted into the DNA sequence.

Question 14

What is a single gene deletion mutation?

Answer 14

They involve a nucleotide being left out or deleted from the DNA sequence.

Question 15

What does both single gene insertion and deletion mutations result in?

Answer 15

Frame-shift

Question 16

What is a frame-shift mutation?

Answer 16

When all of the codons and all of the amino acids after the mutations get changed. This has a major effect on the structure of the protein produced.

Question 17

What is a chromosome structure mutation?

Answer 17

It involves a change in the structure or number of chromosomes.

Question 18

What are the 4 types of chromosome mutations?

Answer 18

Deletion, inversion, translocation, and duplication.

Question 19

What happens during a deletion chromosome mutation?

Answer 19

Where a chromosome breaks in two places and section becomes detached. Two ends attach to give a shorter chromosome.

Question 20

What are the effects of a deletion chromosome mutation?

Answer 20

Effects are usually drastic as genes have been lost.

Question 21

What are the effects of a chromosome inversion mutation?

Answer 21

Chromosome breaks in two places and the middle piece turns around so that the normal gene sequence in that part is reversed.

Question 22

What is a chromosome translocation reaction?

Answer 22

Where a section of a chromosome is added to a different chromosome, not its homologous partner.

Question 23

What is a chromosome duplication reaction?

Answer 23

Where a section of a chromosome is added to/from its homologous partner.

Question 24

What are the effects of a chromosome duplication reaction?

Answer 24

These can happen without harming the individual because there is still one good copy of the gene. It may be a source of variation for the species as the extra gene may undergo beneficial point mutation. These can sometimes be detrimental, e.g. it can cause cancer.

Question 25

What is the importance of mutations and gene duplications in evolution?

Answer 25

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