Substitution of nucleotides mutation

Question 1

Substitution of nucleotides is a mutation where

Answer 1

A mutation that occurs when a base in the DNA sequence is randomly swapped for a different base

Question 2

Unlike an insertion or deletion mutation, a substitution mutation will only change

Answer 2

the amino acid for the triplet (a group of three bases) in which the mutation occurs; it will not have a knock-on effect

Question 3

Substitution mutations can take three forms:

Answer 3

silent mutation

missense mutation

Nonsense mutation

Question 4

Silent mutations are

Answer 4

the mutation does not alter the amino acid sequence of the polypeptide (this is because certain codons may code for the same amino acid as the genetic code is degenerate)

Question 5

missense mutations are

Answer 5

the mutation alters a single amino acid in the polypeptide chain (sickle cell anaemia is an example of a disease caused by a single substitution mutation changing a single amino acid in the sequence

Question 6

nonsense mutations are

Answer 6

the mutation creates a premature stop codon (signal for the cell to stop translation of the mRNA molecule into an amino acid sequence), causing the polypeptide chain produced to be incomplete and therefore affecting the final protein structure and function (cystic fibrosis is an example of a disease caused by a nonsense mutation, although this is not always the only cause)