What are the different types of point mutation?

Point mutation is a type of genetic mutation where a single nucleotide base in a DNA sequence is changed, altered or deleted. Point mutations can be differentiated into two main categories based on substitution of base pairs and the effects the mutation produced. 

Based on substitution of base pairs, point mutations may be grouped into two types:  

• Transition mutations, in which a pyrimidine or purine base is substituted by another pyrimidine or purine base, resulting in a different set of base pairs
• Transversion mutations, in which a pyrimidine based is substituted by purine base or vice versa 

Based on effects produced by the changes in base pairs, point mutations may be grouped into three types: 

• Nonsense mutations, in which the substitution of a base pair results in a premature stop codon, which stops the protein from being synthesized and results in the production of nonfunctional or shortened proteins 
• Missense mutations, in which the substitution of a base pair changes the amino acid present in the resulting protein, which may have no effect or result in a nonfunctional protein depending on the type of substitution and the position of substitution 
• Silent mutations, in which the substitution causes no observable effect on the organism’s phenotype because the amino acid sequence generated after the alteration and the original amino acid sequence are mostly similar
• Frameshift mutations, where nucleotides of a DNA sequence are altered in a way that changes one or more codons.