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.

Verified step by step guidance

1. Understand the role of enzymes in biological reactions: Enzymes are biological catalysts that speed up chemical reactions without being consumed in the process. In this case, the enzymes are responsible for breaking down DNA by catalyzing the hydrolysis of covalent bonds.
2. Identify the structure of DNA: DNA is composed of two strands forming a double helix. Each strand is made up of nucleotides, which consist of a phosphate group, a deoxyribose sugar, and a nitrogenous base (either a purine or pyrimidine).
3. Focus on the covalent bonds in DNA: The covalent bonds that join nucleotides together are known as phosphodiester linkages. These linkages form the backbone of the DNA strand, connecting the phosphate group of one nucleotide to the deoxyribose sugar of the next nucleotide.
4. Determine the effect of enzyme action: When enzymes catalyze the hydrolysis of phosphodiester linkages, they break the covalent bonds in the DNA backbone. This results in the fragmentation of the DNA strand into individual nucleotides or smaller nucleotide chains.
5. Evaluate the options: Given that the enzymes break the phosphodiester linkages, option b is correct. The DNA backbone is disrupted, but the bases remain attached to their respective deoxyribose sugars, ruling out options c and d. The separation of the two strands (option a) involves breaking hydrogen bonds, not covalent bonds.

Key Concepts

Enzyme Function

Enzymes are biological catalysts that speed up chemical reactions without being consumed in the process. They work by lowering the activation energy required for a reaction, allowing it to proceed more quickly. In the context of DNA, specific enzymes can catalyze the hydrolysis of covalent bonds, breaking down the DNA structure.

DNA Structure

DNA is composed of two strands forming a double helix, with each strand consisting of a sugar-phosphate backbone and nitrogenous bases. The backbone is formed by phosphodiester linkages between nucleotides, while the bases pair through hydrogen bonds. Understanding this structure is crucial to predicting the effects of enzymatic action on DNA.

Hydrolysis Reaction

Hydrolysis is a chemical reaction involving the breaking of bonds in molecules using water. In the case of DNA, hydrolysis can break the phosphodiester linkages in the backbone, leading to the separation of nucleotides. This process is essential for understanding how enzymes can degrade DNA by cleaving these covalent bonds.