Which of the following is the most effective chemical mutagen?

The following diagram shows two chromosomes and the letters represent the genes.
Chromosome $1$:

$P$

$Q$

$R$

$S$

$T$

$U$

$V$

$W$

Chromosome $2$:

$E$

$F$

$G$

$H$

Which of the following would result if a translocation occurred between chromosome $1$ and $2$?

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

Hugo de Vries worked on which plant and proposed the idea of mutation?

Mutation rates are affected by

Mutation is an error that occurs during cell division.