<span>A mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements.
The most frequent kind of mutation, a point mutation, occurs when a single base pair is replaced by another.</span>
Explanation: The Dobson Unit is the most common unit for measuring ozone concentration. Becuse ozone concentration is hard to measure they use The Dobson Unit.
