The reason for fault in gene duplication is

Which mutation causes a change in an allele?

What is the cause of a point mutation?

Which base is responsible for spontaneous point mutations?

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 $2$?

The primary source of allelic variation is