14.4 - Gene Mutation

What is gene mutation?

Any change to the quantity or structure of the DNA of an organism is known as a mutation.
Any change to one or mole nucleotide bases, or any rearrangement of the bases, in DNA is known as a gene mutation.

Substitution of Bases

The type of gene mutation in which a nucleotide in a DNA molecule is replaced by another nucleotide that has a different base is known as a substitution.

• A nonsense mutation occurs if the base change results in the formation of one of the three stop codons that mark the end of a polypeptide chain.
• A mis-sense mutation arises when the base change results in a different amino acid being coded for. The polypeptide produced will differ in a single amino acid. If this amino acid is important in forming bonds that determine the tertiary structure of the protein, the replacement amino acid may not form the same bonds. The protein may then be a different shape and not function properly e.g. enzymes cannot form enzyme-substrate complex.
• A silent mutation occurs when the substituted base still codes for the same amino acid due to the degenerate…