When a base substitution mutation occurs, one nucleotide in a replicating DNA sequence is substituted for another, which results in the production of a mutant strand of DNA. The result of the mutation depends on how the substituted nucleotide base alters the string of amino acids coded by the mutant DNA. The three types of base substitution mutations are nonsense mutations, missense mutations, and silent mutations. Each type is defined by how it affects protein synthesis. a) silent mutation
b) nonsense mutation
c) missense mutation
d) frameshift mutation

A. Silent mutation:

Silent mutations are considered as mutation in DNA which do not have any effect on phenotype of organism. It comes in the category of neutral mutation.

It occurs when single DNA nucleotide change within protein coding sequence of a gene but does not change the sequence of amino acid to make protein.

B. Nonsense mutation:

Nonsense mutation is defined as the mutation of single base pair which changes the specific amino acid codon into stop codon. This stop codon is called the premature stop codon and at the result the protein structure will be shortened and most likely non-functional.

C. Missense mutation:

A single nucleotide mutation occurs in the sequence of gene which can lead to substitution of amino acid in resulting protein is known as missense mutation.

D. Frameshift mutation:

A frameshift mutation is considered as the genetic mutation caused by indels (deletions or insertions) in DNA nucleotide sequence which leads to shift the way the sequence is read.

3 bases group is considered as reading frame which code of amino acid. In frameshift mutation due to addition or deletion of bases these groups of bases changes/shift which lead to change in code for amino acid.

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