Lecture 19 Effects of Mutations I

Question 1

Define deletion mutation

Answer 1

Deletion mutation is a mutation resulting from deletion of one or more base pairs from a DNA sequence.

Question 2

Define a frameshift mutation

Answer 2

A mutation that results from insertion or deletion of a group of base pairs that is not a multiple of three and which therefore changes the frame in which translation occurs.

Question 3

Define insertion mutation

Answer 3

A mutation that arises by insertion of one or more base pairs into a DNA sequence.

Question 4

Define inversion

Answer 4

A mutation which involves excision of a portion of a DNA molecule followed by re-insertion at the same position but in the reverse orientation.

Question 5

Define nonsense mutation.

Answer 5

An alteration in the nucleotide sequence that changes the triplet codon for an amino acid into a termination codon.

Question 6

Define non-synonomous mutation

Answer 6

This is a mutation that changes the amino acid sequence of a protein.

Question 7

Define point mutation

Answer 7

a mutation that results from a single base pair change in a DNA molecule

Question 8

Define readthrough mutation

Answer 8

A mutation that changes a termination codon into a codon specifying an amino acid, and hence results in readthrough of the termination codon.

Question 9

Define second site reversion

Answer 9

a second mutation that reverses the effect of a previous mutation in the same gene but does not restore the original nucleotide sequence.

Question 10

Define silent mutation

Answer 10

A change in the DNA sequence that has no effect on the expression or functioning of any gene or gene product.

Question 11

Define synonymous mutation

Answer 11

a mutation that does not alter the protein chain.

Question 12

Explain what is meant by a transition

Answer 12

This is a point mutation that replaces a purine with another purine, or a pyridmidine with another pyrimidine.

Question 13

Explain what is meant by a transversion

Answer 13

A point mutation that involves a purine being replaced by a pyrimidine or vice versa.

Question 14

What is the difference between a transition and a transversion mutation

Answer 14

A transition mutation occurs when a purine is switched with another purine. It is a point mutation.A transversion is a point mutation where a purine is switched with a pyrimidine.

Question 15

Explain why nonsene and frameshift mutations are more likely to result in an altered protein

Answer 15

frameshift mutations occur due to insertion of nucleotides (not multiple of 3) which changes the frame in which the protein is read.