Which one is used as a vector in genetic engineering?

$A$ : Ethidium bromide helps in visualizing $DNA$ in $UV$ light only.
$R$ : This intercalating agent absorbs light in range $260-330 \; nm$.

The enzyme that is used in $PCR$ technology is:

An extra-chromosomal self-replicating part of the cell that has proven to be a boon to biotechnology is

What is a palindromic sequence?

The first restriction endonuclease type $II$,$...A..$,was isolated by Smith,Wilcox and Kelley from $...B...$ bacterium. It was found to cut $DNA$ molecules at a particular point by recognizing a specific sequence of six base pairs,known as the $...C....$. Here $A, B$ and $C$ can be: