What is referred to as the "backbone" of DNA?

The "backbone" of DNA refers to the structural framework that provides stability and support to the DNA molecule. It is composed of alternating sugar and phosphate groups. In the case of DNA, the sugar involved is deoxyribose, which is a five-carbon sugar. The backbone is crucial because it forms the repeating structural unit that supports the nitrogenous bases attached to it.

Since the correct answer includes both phosphate and deoxyribose, it highlights the specific components that make up the backbone of DNA, distinguishing it from RNA, which contains ribose instead of deoxyribose. The combination of the phosphate group with the deoxyribose sugar creates a strong and stable structure that allows the DNA to maintain its double helix shape while providing a place for the nitrogenous bases to attach. This structure is fundamental to DNA's function in genetic encoding and transmission.