In gel electrophoresis,the $DNA$ fragments separate according to ........

The blue and white selectable markers have been developed which differentiate recombinant colonies from non-recombinant colonies on the basis of their ability to produce colour in the presence of a chromogenic substrate.
Given below are two statements about this method :
Statement-$I$ : The blue coloured colonies have $\text{DNA}$ insert in the plasmid and they are identified as recombinant colonies.
Statement-$II$ : The colonies without blue colour have $\text{DNA}$ insert in the plasmid and are identified as recombinant colonies.
In the light of the above statements,choose the most appropriate answer from the options given below:

Silencing of specific mRNA in RNAi is by

Recombinant $\text{DNA}$ is directly injected into the nucleus of an animal cell by $-$

$A$ transformed bacterium with a human gene fails to produce the desired protein. The reason could be:

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