The right answer is the third one
A point mutation is a change in the structure of the gene, affecting one to several nucleotides (between one and ten).
There are four types of point mutations:
* substitution: which is the replacement of one (or more) nucleotides.
* insertion : which is the addition of one or more nucleotides;
* deletion : which is the loss of one or more nucleotides.
* inversion: which is the permutation of 2 neighboring deoxyribonucleotides;
