1.4 mutations

Question 1

State the definition of a mutation

Answer 1

A mutation is a random change in the DNA sequence of an organism.

Question 2

Identify the three main types of gene mutation and describe how the DNA is changed in each case

Answer 2

The three main categories of gene mutations are : S.I.D.
· Substitution
· Insertion
· Deletion

Question 3

What is substitution

Answer 3

· Substitution – replacement of one nucleotide base with another nucleotide base

Question 4

What is insertion

Answer 4

· Insertion – addition of an extra nucleotide base into the gene sequence.

Question 5

What is deletion

Answer 5

· Deletion – removal of a nucleotide base from the gene sequence.

Question 6

identify the three main types of substitution mutation

Answer 6

missense
nonsense
splice site

Question 7

What is missense and whats the impact it has on the protein produced?

Answer 7

change to the nucleotide base code for one amino acid being changed. This has a minor impact as only one amino acid is changed in the protein. It can result in a non functional protein or have little effect on the protein.

Question 8

What is nonsense and whats the impact it has on the protein produced?

Answer 8

Has a major impact as a codon that should code for an amino acid is replaced by one that acts a premature stop codon

Question 9

What is splice site and what impact does it have on the protein produced?

Answer 9

some introns being retained and/or some exons not being included in the mature transcript. This can have a significant impact on the shape and therefore the function on the protein produced

Question 10

Identify the types of gene mutation that are described as frameshift mutations.

Answer 10

Insertion and deletion gene mutations will both cause frame-shift mutations.

Question 11

Explain the term frameshift mutation

Answer 11

It causes the reading frame of the codons to be changed by either the insertion or deletion of a nucleotide base.

Question 12

What does frameshift mutation result in

Answer 12

all of the codons to be ‘read’ during translation after the point of the mutation being changed. Therefore, all of the amino acids produced after the point of mutation will be changed.

Question 13

What effect does frameshift mutation have

Answer 13

This has a major effect on the structure of the protein produced because an entirely different sequence of amino acids will be produced within the polypeptide chain, which will have a major effect on the shape of the final protein.

Question 14

Identify the four types of chromosome structure mutations.

Answer 14

(D.D.I.T)
Deletion
Duplication
Inversion
Translocation

Question 15

Describe duplication

Answer 15

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

Question 16

Describe deletion

Answer 16

This is where a chromosome breaks in two places and the middle segment is detached

Question 17

Describe inversion

Answer 17

The chromosome breaks in two and the segment turns around and reattaches

Question 18

Describe translocation

Answer 18

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

Question 19

Explain why chromosome structure mutations are more significant in terms of health than gene mutations.

Answer 19

Chromosome structure mutations are more likely to be lethal and therefore more significant in terms of health than gene mutations because chromosome structure mutations typically involve changes to multiple genes so potentially affect the production of many proteins within an organism

Question 20

What can a mutation result in?

Answer 20

no protein, or an altered protein being synthesised instead of the normal protein. Mutations occur rarely and spontaneously, they cannot be predicted, and they can affect single genes or entire chromosomes.