Lecture 9

Question 1

What is a mutation?

Answer 1

Heritable changes to DNA sequence
Caused by
- errors in replication (rare because of repair and proof reading)
- physical (uv radiation and X Rays)
- chemical mutagens (ethidium bromide)
- viral mutagens (HPV)

Question 2

What are the types of mutation?

Answer 2

Substitution - one base pair changed
Deletion- one or more base pairs missing
Insertion - one or more base pairs added
Inversion - two or more base pairs reversed
Translocation - piece of DNA moved from one site to another
Duplication - piece of DNA is repeated

Question 3

What is point mutation?

Answer 3

Largely historical term

• refers to mutation that behaves as a single point in classical genetic crosses
• only a small region (few bp) of DNA involved

Question 4

What are the effects of the varying types of mutations?

Answer 4

Substitution - only affects one amino acid (unless it mutates to a stop codon)
Deletion/insertion - frame shift, can affect the whole protein sequence after the mutation site
Inversion - effect depends on size of inversion
Translocation - may have no immediate effect
Duplication - frame shift

Question 5

What is a frame shift mutation?

Answer 5

Insertion or deletion of nucleotides other than multiples of three

• changes reading frame
• alters all the amino acids in the protein beyond this point
• structure and function of protein changed

Question 6

What are transposable genetic elements?

Answer 6

Segments of DNA that can move around within/between DNA molecules
Can bring about insertion, translocation and duplication mutations
Potent agents of mutation
Important agents of genome plasticity

Question 7

What are the two levels of mutation?

Answer 7

Chromosome changes (aberrations)
Gene mutations