Problem:

Question 1: Which is not a difference between B-DNA and A-DNA?

a. A-DNA forms under more dehydrating conditions than B-DNA.
b. For polynucleotide strands containing the same number of nucleotides, the A-DNA strand will be shorter from end-to-end than the corresponding B-DNA.
c. Both are helical, but B-DNA is right-handed and A-DNA is left-handed.
The planes of the nitrogenous bases are not perpendicular to the helix axis in A-DNA.

Question 2: Supercoiling of pure circular DNA is a result of ________.

a. underwinding or overwinding of the helix
b. entanglements because of the long length of the strands
c. the lack of associated histones
d. the activity of exonucleases

Question 3: What is the function of DNA toposiomerases?

a. cleaving nucleotides from the ends of DNA
b. adding or removing supercoils
c. methylation of the nitrogenous bases
d. packaging of DNA into nucleosomes

Provide the correct answer and justification for your choice.