Which enzyme joins the broken strands of $DNA$?

$A$ single-stranded piece of nucleic acid tagged with a radioactive molecule,which is used to detect a specific gene through hybridization,is called:

Discuss with your teacher and find out how to distinguish between (Any two):
$(a)$ Plasmid $DNA$ and Chromosomal $DNA$
$(b)$ $RNA$ and $DNA$
$(c)$ Exonuclease and Endonuclease

In case of $BamHI$,$H$ represents

Polymerase chain reaction employs

Which one of the following is regarded as a natural genetic engineer?