Known sequence of $DNA$ that is used to find a complementary $DNA$ strand is:

$I.$ Bacteriophages are $...A...$ infecting $...B....$
$II. ...C...$ are hybrid vectors derived from plasmids which contain $cos$ site of $\lambda$ phage.
$A, B$ and $C$ in above statements refer to:

Microbes found to be very useful in genetic engineering are

Which of the following is known as a natural genetic engineer?

The $Ti$ plasmid is frequently used in plant transformation. This plasmid is found in .......

Which of the following enzymes are used to join bits of $DNA$?