Would you choose an exonuclease, while producing a recombinant DNA molecule?
No, as exonuclease acts on the free ends of linear DNA molecule. Therefore, instead of producing DNA fragments with sticky ends, it will shorten or completely degrade the DNA fragment containing the gene of interest and the circular plasmid (vector) will not get cut as it lacks free ends.
What does $H$ in ' $d$ ' and III refer to the enzyme Hind III?
(i) The first letter ' $H$ ' indicates the genus of the organism from which the enzyme was isolated, $H=$ genus Haemophilus.
(ii) The fourth letter $d$ indicates the particular strain used to produce the enzyme, $d=$ strain Rd.
(iii) The Roman numerals denoted the sequence in which the restriction endonuclease enzyme from that particular genus, species and strain of bacteria have been isolated-III, i.e., third restriction endonuclease to be isolated from this species.
Restriction enzymes should not have more than one site of action in the cloning site of a vector. Comment.
If the restriction enzymes have more than one recognition site in a vector, then the vector itself will get fragmented on treatment with the restriction enzymes.
What does 'competent' refer to in competent cells used in transformation experiments?
DNA being a hydrophilic molecule can not pass through cell membranes. Therefore, the bacteria should be made competent to accept the DNA molecules.
Competent means bacterial cells, on treatment with chemicals like $\mathrm{CaCl}_2$, are made capable of taking up foreign DNA.
What is the significance of adding proteases at the time of isolation of genetic material (DNA)?
Proteases degrade the proteins present inside a cell (from which DNA is being isolated). If the proteins are not removed from DNA preparation then they could interfere with any downstream treatment of DNA.