Mutations

Question 1

Define mutation.

Answer 1

A change in DNA sequence that affects genetic information.

Question 2

When do most mutations occur in the cell cycle?

Answer 2

During DNA replication - interphase.

Question 3

What are the 3 steps in DNA replication?

Answer 3

Initiation.
Elongation.
Termination.

Question 4

What happens during initiation?

Answer 4

DNA helicase unwind the DNA by breaking H-bonds.

Question 5

What happens during elongation?

Answer 5

New DNA strand ‘grows’ 1 base at a time with the primer acting as the leading strand’s starting point.

Question 6

What happens during termination?

Answer 6

Fragments terminate in an RNA primer and are removed by DNA exonucleases. Complementary nucleotides are added to the gaps.

Question 7

What enzyme is involved in initiation?

Answer 7

DNA helicase.

Question 8

What enzyme is involved in elongation?

Answer 8

DNA polymerase (it controls elongation).

Question 9

What enzymes are involved in termination?

Answer 9

Primase produces the primers needed. DNA exonucleases remove fragments. DNA ligase adds phosphate to gaps.

Question 10

1 chromosome

=

Answer 10

1 chromosome

2 chromatids

Question 11

What is produced during mitosis?

Answer 11

2 identical daughter cells.

Question 12

What is produced during meiosis?

Answer 12

4 differing haploid daughter cells.

Question 13

What are the 2 types of substitution mutations?

Answer 13

Transitions and transversions.

Question 14

What is a transition mutation?

Answer 14

A substitution mutation where a purine is swapped for a purine or a pyrimidine for a pyrimidine.

Question 15

What is a transversion mutation?

Answer 15

A substitution mutation where a purine is swapped for a pyrimidine and vice versa.

Question 16

What is the difference between missense, nonsense and silent mutations?

Answer 16

Missense results in an amino acid change, nonsense results in a STOP codon and silent has no amino acid change.

Question 17

Missense mutation

=

Answer 17

Missense mutation

Nonsynonymous substitution

Question 18

Silent mutation

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Answer 18

Silent mutation

Synonymous substitution

Question 19

Where does the term nonsynonymous substitution come from?

Answer 19

Because there is a change in the nucleotide but no change in the

Question 20

What is an example of a point mutation in disease? What is the specific change?

Answer 20

Sickle cell disease. Thymine is replaced by adenine leading to a synonymous substitution - Glu changes to Val.

Question 21

What 5 mutations cause frameshift?

Answer 21

Insertion, deletion, duplication, inversion and translocation.

Question 22

What is an example of a frameshift mutation in disease? What is the specific change?

Answer 22

Tay Sachs disease. A 4 nucleotide insertion on chromosome 15.