Gene + Chromosomes Mutations

Gene Mutation

• Change in DNA base sequence

• Occur spontaneously during DNA replication but radiation, chemicals and viruses can increase risk of a mutation

• 3 Types - Substitution, Deletion and Insertion

• lead to a change in amino acid sequence and a different polypeptide

Substitution

• One base is swapped with another

• Not all substitutions lead to a change of amino acid due to the degenerate nature of genetic code, many amino acid are coded for by more than one triplet

• However some triplets do code for different amino acids and the structure of the resulting protein is changed

Deletion

• more likely to cause a change in amino acid sequence because every amino acid after the deletion changes

• All bases move one to left

• More serious than substitution mutations

Insertion

• A base is added to triplet

• Moves all bases after insertion one to the right

• Changes all amino acids after the deletion

Chromosome mutations

• Chromosome mutations involve changes to the structure or number of whole chromosomes. Arise spontaneously through errors in cell division