Silencing of specific mRNA in RNAi is by

In gel electrophoresis,the separated $DNA$ fragments are visualized after staining the $DNA$ with $...A...$ followed by exposure to $...B...$. Here $A$ and $B$ refer to:

Which of the following is $NOT$ an application of $PCR$ (Polymerase Chain Reaction)?

The presence of a chromogenic substrate gives ............ coloured colonies.

Why are stirred-tank bioreactors specifically designed?

Having become an expert on gel electrophoresis,you are asked to examine a gel for a colleague. Where would you find the smallest segment of $DNA$?