Which of the following diagnostic tools allows the detection of very low concentration of bacteria or viruses by amplifying their nucleic acid?

$A$ bioreactor is

If a recombinant $DNA$ bearing a gene for resistance to Ampicillin is transferred into $E. coli$ cells,the host cells become transformed into Ampicillin-resistant cells. What happens when these $E. coli$ are grown on a medium containing Ampicillin?

Diagrammatically represent the experimental steps in cloning and expressing a human gene (e.g.,the gene for growth hormone) in a bacterium like $E. coli$.

The cutting of $DNA$ by restriction endonucleases results in the fragments of $DNA$. These fragments can be separated by a technique known as ......

Which one of the following statements is not true regarding the gel electrophoresis technique?