DNA Ligase o What is the role of DNA Ligase in replication? o What are the two s
ID: 193116 • Letter: D
Question
DNA Ligase o What is the role of DNA Ligase in replication? o What are the two steps in the reaction mechanism of DNA Ligase? Briefly describe the reaction mechanism.
• Termination of Replication
o What are Tus and Ter? Describe their role in the termination of replication.
o What does it mean that Tus-Ter sites are directional?
o What role does Topoisomerase IV play in the termination of replication?
What type of topoisomerase is Topoisomerase IV?
o What is the role of telomerase in the termination of eukaryotic replication?
Describe how telomerase synthesizes a single strand of DNA.
Describe how the strand of DNA synthesized by telomerase is converted to a DNA double helix. Be sure to name the enzymes involved and what they do.
What are the functions of TRF and telomere duplex binding proteins?
What are the functions of the telomere segment of DNA?
• How does acyclovir stop a viral infection? o Would ddCTP be as effective? o Can acyclovir also be used as a chemotherapeutic agent? o Name the class of compounds to which Acyclovir belongs
Explanation / Answer
1) DNA ligase is an enzyme that joins fragmented DNA in DNA replication. The enzyme forms two covalent phosphodiester bonds between 3' hydroxyl ends of one nucleotide, with the 5' phosphate end of another. In bacteria, the DNA ligase follows a reaction mechanism with two steps - The reversible adenylation of ligase with NAD+ as the adenylyl donor. In the second step, ligase transfers the AMP to the 5 phosphate end of nicked duplex DNA and finally catalyzes nick closure and the releases AMP.
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