In which type of bioreactor do air bubbles increase the oxygen transfer area?

Silencing of specific mRNA in RNAi is by

$I. ... A...$ is the ability of a cell to take up foreign $DNA$.
$II.$ The cell is treated with a specific concentration of a divalent cation such as $... B...$ to increase the pore size in the cell wall.
$III.$ In $...C...$ method,recombinant $DNA$ is directly injected into the nucleus of an animal cell.
The most appropriate option regarding $A, B$ and $C$ is:

Which of the following is not present in a bioreactor?

Which of the following components are used in gel electrophoresis?
$I.$ Ethidium bromide
$II.$ Restriction endonuclease
$III.$ Agarose
$IV.$ $UV$ radiation
Choose the correct option:

The separated bands of $DNA$ are cut out from the agarose gel and extracted from the gel piece. This step is known as . . . . . . .