Hugo de Vries proposed the Mutation theory by studying the plant called . . . . . . .

Given below is the representation of a kind of chromosomal mutation. What is the kind of mutation represented?

$...$ is a phenomenon by which genetic variation is achieved through changes in the base sequences within genes,which creates a new character or trait absent in the parental generation.

Assertion: An organism with lethal mutation may not even develop beyond the zygote.
Reason: All types of gene mutations are lethal.

Mutations generally result in .......

Which one of the following mutations partially or fully reverses the harmful effects of a previous mutation?