Academic Integrity: tutoring, explanations, and feedback — we don’t complete graded work or submit on a student’s behalf.

DNA ligase has the ability to relax supercoiled circular DNA in the presence of

ID: 207487 • Letter: D

Question

DNA ligase has the ability to relax supercoiled circular DNA in the presence of AMP but not in its absence.

Part A:

What is the mechanism of this reaction, and why does it depend on AMP?

d) To relax supercoil DNA ligase inserts AMP in the tensest place that creates the axis of rotation.

Part B: How could you determine that supercoiled DNA had in fact been relaxed?

a) Analyze the DNA by electron microscopy.

b) Analyze the DNA by spectrophotometry.

c) Analyze the DNA by fluorimetry.

d) Analyze the DNA by gel electrophoresis.

e) Analyze the DNA by X-ray.

a) After production of single-strand interruption DNA ligase needs base to restore DNA sequence. b) The DNA ligase reaction uses AMP as an energy carrier during relaxation supercoiled DNA. c) The DNA ligase needs AMP for the DNA-adenylate intermediate for single-strand interruption to be made.

d) To relax supercoil DNA ligase inserts AMP in the tensest place that creates the axis of rotation.

Part B: How could you determine that supercoiled DNA had in fact been relaxed?

a) Analyze the DNA by electron microscopy.

b) Analyze the DNA by spectrophotometry.

c) Analyze the DNA by fluorimetry.

d) Analyze the DNA by gel electrophoresis.

e) Analyze the DNA by X-ray.

Explanation / Answer

Part A:

What is the mechanism of this reaction, and why does it depend on AMP?

c) The DNA ligase needs AMP for the DNA-adenylate intermediate for single-strand interruption to be made.

Part B: How could you determine that supercoiled DNA had in fact been relaxed?

a) Analyze the DNA by electron microscopy.