The concept of sudden genetic change which breeds true in an organism is visualised in the principle of

Agents that induce mutations are called ....

The rate of appearance of new forms is linked to which of the following?

Duplication of one or two bases of $DNA$ produces . . . . . . .

The following characteristics are most suitable for which of the following processes?
$(i)$ Due to alteration of $DNA$ sequences,the genotype is changed.
$(ii)$ Changes occur in the phenotype.
$(iii)$ Variation is created in $DNA$.

Which of the following is the best mutagen for microorganisms?