8.1 DNA and the Structure of Proteins

Question 1

What is a mutation?

Answer 1

• An alteration to the DNA base sequence
• Often arise spontaneously during DNA replication

Question 2

What are addition and deletion mutations?

Answer 2

Where one or more nucleotides are either inserted or deleted from the DNA sequence

Question 3

What is a substitution mutation?

Answer 3

Where one nucleotide base in the DNA sequence is replaced by another

Question 4

What is a duplication mutation?

Answer 4

Where one or more nucleotide bases duplicate and repeat

Question 5

What is an inversion mutation?

Answer 5

Where a group of nucleotide bases become separated from the DNA sequence, then rejoin in the reverse order i.e. they have flipped

Question 6

What is a translocation mutation?

Answer 6

Where a group of nucleotide bases become separated from the DNA sequence, and are then inserted into the DNA of a different chromosome

Question 7

Which mutations are most likely to have a significant impact and why?

Answer 7

• Insertion, deletion, duplication, translocation
• Because they produce a frameshift, meaning the entire amino acid sequence produced will be different

Question 8

Which mutations are most likely to have a smaller impact and why?

Answer 8

• Substitution, inversion
• They only alter one or very few triplets, the amino acid sequence may not be affected due to the degenerate nature of the genetic code

Question 9

Is a mutation resulting in a change to the amino acid sequence always harmful?

Answer 9

• No
• May be neutral if the resulting change in protein has no effect on the organism
• May also be beneficial, which is the basis for evolution and natural selection

Question 10

What is a mutagenic agent?

Answer 10

Factors that increase the rate of gene mutation

Question 11

Examples of mutagenic agent

Answer 11

• Chemical mutagens such as alcohol and benzene
• Ionising radiation such as UV and x-ray