3.8.1

Question 1

What are the 3 gene mutations resulting in a frameshift?

Answer 1

• deletion. Base deleted.
• addition. Base added.
• duplication. Same base added.

Question 2

What doesn’t happen when three bases are added or deleted?

Answer 2

no frameshift- reading frame will stay the same

Question 3

What gene mutations aren’t usually associated with a frameshift?

Answer 3

• substitution.
• inversion. Bases swapped.
• translocation. Bases moved.

Question 4

What are the 3 effects of a substitution mutation?

Answer 4

• non-sense. Stop codon created so non-functional protein
• mis-sense. Different amino acid coded for so different functional protein
• silent. Same amino acid coded for because genetic code is degenerate

Question 5

Give examples of mutagens

Answer 5

• High energy and ionising radiation (x-rays, UV, alpha and beta particles)
• chemicals: nitrous dioxide NO2 (change DNA structure), benzophyrene (activates tumour suppressor gene)

Question 6

How and when do gene mutations occur?

Answer 6

• spontaneously
• mutation rate increased by mutagenic agents
• during s-phase of interphase where DNA is replicated by semi-conservative replication