Such types of mutation affects only a single nucleotides or few nucleotides. These can be further subclassified into; Substitution mutation, Deletion mutation and Insertion mutation. When a nucleotide is replaced with another nucleotide it is called as Substitution mutation. Example of substitution mutation are
• Pyrimidine replaced by purine(T-G)
• Purine replaced by another purine (A-G)
• Pyrimidine substituted by another pyrimidine (T-C)
• Purine replaced by pyrimidine (G-T)
The first and the last mutation are transversion type of mutation. The other two are transition types of mutation.
Point mutation is also referred to substitution mutation, when involves a single nucleotide or gene. There are various types of point mutation.
When there is shift in nucleotide bases due to addition or removal of nucleotides, it is called as Frame shift mutation, thus creating an issue while translating the mRNA into proteins.
In nonsense mutations, a protein is formed which is not complete and is very small. Example Cystic fibrosis.
Missense mutations occurs when, a single nucleotide is removed or added, thus leading to change in the base pair, thus from the amino acids a different protein would be formed than the required one.
A mutation with no positive and negative effect is called as neutral mutation.
A mutation in which no changes are seen in the amino acid, however, the protein functions is called as Silent mutation.