If the gene sequence on a chromosome changes from $abcdefg$ to $abcfedg$,what is this phenomenon called?

In nature,the occurrence of mutations is:

$...$ 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.

$A$ sudden and distinct change that occurs in the genetic makeup is called ......

Which of the following parental combinations has produced a mutant offspring?

Haploids are more suitable than diploids for the study of mutations because .........