SF1: DNA mutagenesis and mutation detection

Question 1

What are the three components of DNA? Which of these can be damaged?

Answer 1

1. Bases (bonded with weak hydrogen bonds)
2. Sugar ring (in the backbone)
3. Phosphate group (in the backbone)

They can all be damaged.

Question 2

What makes up a nucleotide?

Answer 2

DNA bases and the sugar-phosphate backbone

Question 3

Define ‘DNA mutation’

Answer 3

A change in DNA sequence or rearrangement of genetic material

Question 4

What are the two reasons why a person has a DNA mutation?

Answer 4

Inheritied

• Through parental germline, so passed on to offspring
• e.g. people who have been exposed to radiation can pass mutations to offspring who were never exposed

Acquired

• ​Somatic cells
• Can accumulate and become malignant

Question 5

What are the two main types of DNA mutation? Define them.

Answer 5

Micromutations – a change in the DNA sequence

Macromutations – rearrangements of genetic material

Question 6

What are the three types of micromutation?

Answer 6

• Deletion
• Insertion
• Substitution

Question 7

What are the five types of macromutation?

Answer 7

• Deletion
• Duplication
• Inversion
• Substitution
• Translocation

Question 8

What are the five types of DNA mutation?

Answer 8

• Silent
• Missense
• Nonsense
• Frameshift
• Gross change

Question 9

What effects can a mutation in the non-coding region of DNA have?

Answer 9

• Change product amount
• Change product activity
• No effect

Question 10

Describe a silent mutation

Answer 10

A change in the base does not lead to a change in the amino acid sequence or protein due to the degenerate nature of DNA

Question 11

Define ‘missense mutation’

Answer 11

A mutation that changes an amino acid to another amino acid

Question 12

Define ‘nonsense mutation’

Answer 12

A mutation that causes a premature stop codon

Question 13

What is a frameshift mutation?

Answer 13

A mutation that results in the loss or gain of multiples of amino acids other than three (e.g. 1, 2, 4, 5, 7)

Question 14

What are four unnatural causes of DNA mutation?

Answer 14

1. Ionising radiations/particles
2. Free radicals
3. Mutagenic agents
4. Anti-cancer agents

Question 15

What is the mechasnism of mutagenesis for unnatural causes of DNA damage such as ionising radiations?

Answer 15

DNA damage → defective or no DNA repair → mutation

Question 16

What spontaneous events can lead to mutation?

Answer 16

• DNA replication errors
• Movement of transposable elements

Question 17

What is the mechanism of mutagenesis for spontaneous events causing DNA damage?

Answer 17

Spontaneous events → mutation

Question 18

How might mutations in parents’ DNA affect their children?

Answer 18

Mutations in the germline will be inherited and may change the phenotype or predisposition in offspring

Question 19

What happens if there’s a mutation in a somatic cell?

Answer 19

There may be a change in the cell phenotype or disease predisposition in the individual