Explanation: Mutations are permanent changes in the nucleotide sequence of a DNA molecule. Substitution leads to a point mutation if only one nucleotide is replaced by another.
A substitution mutation occurs when one or more nucleotides in a DNA sequence is replaced by another nucleotide.
Example of substitution is in sickle cell hemoglobin in which valine replaces glutamate at position six in the two beta chains of hemoglobin. In a normal hemoglobin, the two beta chains of hemoglobin have glutamate at the sixth position but in a sickle cell hemoglobin, valine is found at position six on the two beta chains. This is also an example of a point mutation.
