Give one example in which both physical and chemical changes takes places

A burning candle is a great example.

First the wax melts (physical change).

Then when the melted wax is hot enough, it combines with oxygen in the air, forms carbon monoxide and carbon dioxide, and drifts away as hot gases (chemical change).  

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).

i don't understand. explain it clearly