Enzymes that break down DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes?

a. The two strands of the double helix would separate.

b. The phosphodiester linkages of the polynucleotide backbone would be broken.

c. The pyrimidines would be separated from the deoxyribose sugars.

d. All bases would be separated from the deoxyribose sugars.

The correct answer is option b. "The phosphodiester linkages of the polynucleotide backbone would be broken".

Explanation:

The phosphodiester linkages of the polynucleotide backbone is what binds each nucleotide to each other in the DNA molecules. These linkages are covalent bonds that take place between 3' carbon atom of one sugar molecule and the 5' carbon atom of another. The enzymes that break down DNA catalyze the hydrolysis of the phosphodiester linkage, which results in DNA cleavage within the backbone at specific or unspecific nucleotides.