If DNA molecules are treated with enzymes that specifically break down DNA, the following would happen:
The phosphodiester linkages of the polynucleotide backbone would be broken.
This means that the covalent bonds joining the nucleotides (the phosphodiester bonds) in the backbone of the DNA molecule would be hydrolyzed, resulting in the fragmentation of the DNA strands.
To clarify the other options:
- The two strands of the double helix would separate: This could happen if the hydrogen bonds between the nitrogenous bases were broken, but the question specifically mentions enzymes that break down DNA, which refers to the backbone bonds.
- All bases would be separated from the deoxyribose sugars: This would not happen immediately as the enzymes mentioned are focusing on the backbone rather than the bonds between bases and sugars.
- The pyrimidines would be separated from the deoxyribose sugars: Similar to the previous point, the enzymes break phosphodiester linkages, not specifically the bonds between the pyrimidines (cytosine and thymine) and deoxyribose sugars.
Thus, the correct answer is that the phosphodiester linkages would be broken.