Which phase of drug development is associated with continual evaluation of the drug?

There are three phases of clnic study and one post approval phase required by the Food and Drug Administration (FDA) for a New Drug Application (NDA). Phase IV which is a common stipulation by the FDA includes continual evaluation of the drug after approval has been granted.

Explanation:

1. Topoisomerase is an enzyme helps in over winding Or underwinding of DNA during replication. Helps in the topological correction. So non-functional topoisomerase leads to tangled DNA and prevents replication..

2. Primases are the enzymes helps in the synthesis of short RNA sequences used as primers in replication. Non functional primase leads to no primer synthesis.  

3. DNA Polymerase is an enzyme helps in the addition of new nucleotide to the growing strand in replication. Non functional DNA polymerase prevents the strand growing as no new nucleotides were added.  

4. Helicases are the enzymes helps in the separation of double strands into single and helps in each strand to be copied. Non functional helicase leads to prevention of unwinding of strands and replication inhibition.  

5. ligase is an enzyme that joins nicks(small gaps) in the DNA strand by creating ester bond. Non functional ligase leads to unjointed gaps of lagging strand.  

6. Single strand binding proteins(SSB's) are the small proteins that binds to the single strands of DNA and holds them in a place not to get together while replicating. Non functional SSB's leads to parental strands come back together and prevents replication.