Unit 1-Mutations

Question 1

What is a mutation?

Answer 1

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

Question 2

Mutations can have which two results?

Answer 2

No protein is expressed

or

an altered protein is expressed

Question 3

Are mutations rare and random?

Answer 3

Yes

Question 4

What are mutations the only source of?

Answer 4

Mutations are the only source of new variation in populations.

Question 5

What is a mutant?

Answer 5

An organism that has been affected by and is the result of a mutation.

Question 6

What are the two main types of mutation?

Answer 6

Single gene mutations and chromosome structure mutations.

Question 7

What do single gene mutations involve?

Answer 7

A single gene mutation involves a change in the number or sequence of bases in a gene.

Question 8

What are the three types of gene mutation?

Answer 8

Substitution

Insertion

Deletion

Question 9

What happens in a substitution mutation?

Answer 9

One nucleotide is exchanged for another.

Question 10

What happens in an insertion mutation?

Answer 10

One or more nucleotides added into a DNA sequence

Question 11

What happens in a deletion mutation?

Answer 11

One or more nucleotides removed from a DNA sequence

Question 12

Substitution mutations can be described as a point mutation.
What does this mean?

Answer 12

Point mutations only affect one codon

Question 13

What are the 3 outcomes of substitution mutation?

Answer 13

Missense, Nonsense and Splice-Site.

Question 14

What is meant by a Missense mutation?

Answer 14

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

Question 15

What is the effect on the protein from a Missense mutation?

Answer 15

May result in the shape of the protein changing or may not have any significant effect

Question 16

What is meant by a Nonsense mutation?

Answer 16

A mutation which results in a codon for a specific amino acid being changed to a stop codon.

Question 17

What is the effect on the protein from a Nonsense mutation?

Answer 17

It causes a shorter protein being produced.

Question 18

What is meant by a Splice-Site mutation?

Answer 18

The boundaries between exons and introns are affected (splice sites).

Question 19

What is the effect on the protein from a Splice-Site mutation?

Answer 19

The protein does not function properly.

Question 20

Insertion and deletion mutations can be described as frame-shift mutations.
What is meant by this?

Answer 20

They affect every single codon after the mutation.
Completely different amino acids are coded for from this mutation onwards.

Question 21

What is the effect on the protein from an Insertion mutation?

Answer 21

Every amino acid after the mutation is affected so the protein is usually non-functional.

Question 22

What is the effect on the protein from a Deletion mutation?

Answer 22

Every amino acid after the mutation is affected so the protein is usually non-functional.

Question 23

Why can the broken end of a chromosome join to another broken end?

Answer 23

The broken end of a chromosome is ‘sticky’.

Question 24

What are the 4 types of chromosome structure mutations?

Answer 24

Deletion

Duplication

Inversion

Translocation

Question 25

What happens in a deletion chromosome mutation?

Answer 25

Deletion is where a section of a chromosome is removed.

Question 26

What does a translocation mutation involve?

Answer 26

Translocation is where a section of a chromosome is added to another chromosome that is not its homologous partner

Question 27

What happens in an inversion mutation?

Answer 27

Inversion is where a section of a chromosome is reversed.

Question 28

What happens in a duplication mutation?

Answer 28

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

Question 29

Why can chromosome structure mutations be so lethal?

Answer 29

They often involve such a substantial change to the structure of the chromosome.

Question 30

Mutation occurs continuously and can be spontaneous.
Give an example of something that can cause mutations?

Answer 30

ionising radiation (gamma rays, X-rays and UV light)
or chemical mutagens such as tar from cigarette smoke