8.1 Mutations

Question 1

What is a gene mutation?

Answer 1

• Change in the base sequence of DNA
• Can arise spontaneously during DNA replication

Question 2

What is a mutagenic agent?

Answer 2

Factor that increases rate of mutation (eg. UV radiation)

Question 3

How can a gene mutation lead to the production of a non-functional protein?

Answer 3

• Changes base triplets in DNA so changes sequence of codons in mRNA
• Changes sequence of amino acids
• Changes position of hydrogen/ionic bonds
• Changes tertiary structure

Question 4

Substitution

Answer 4

a base is replaced with another base in DNA

Question 5

Deletion

Answer 5

one or more bases are lost from the DNA base sequence

Question 6

Duplication

Answer 6

a sequence of DNA bases is repeated

Question 7

Inversion

Answer 7

a sequence of DNA bases is reversed

Question 8

Translocation

Answer 8

a sequence of DNA bases detaches and is inserted at a different location within the same or different chromosome

Question 9

Why don’t all gene mutations affect order of amino acids?

Answer 9

• Some substitutions change only one triplet which could code for the same amino acid as the genetic code is degenerate
• Some occur in introns which are removed during splicing

Question 10

Why is a change in amino acid sequence not always harmful?

Answer 10

• May not change tertiary structure of protein
• May positively change properties of protein, giving organism a selective advantage

Question 11

What is meant by a frameshift?

Answer 11

• Occurs when mutations change the number of bases by a number not divisible by 3
• Shifts the way the genetic code is read, altering all triplets downstream