In DNA structure, what is the DNA backbone primarily made of?

• A. Alternating ribose sugars and phosphate groups linked by peptide bonds
• B. A chain of nitrogenous bases connected by hydrogen bonds
• C. Alternating deoxyribose sugars and phosphate groups linked by phosphodiester bonds
• D. A chain of amino acids connected by phosphodiester bonds

Answer: (C)

Verified step by step guidance

1. Understand that the DNA backbone refers to the repeating structural framework of the DNA strand, which supports the nitrogenous bases.
2. Recall that DNA is composed of nucleotides, each containing a sugar, a phosphate group, and a nitrogenous base.
3. Identify the sugar in DNA as deoxyribose, which differs from ribose by lacking one oxygen atom.
4. Recognize that the backbone is formed by alternating deoxyribose sugars and phosphate groups connected through phosphodiester bonds, which link the 3' carbon of one sugar to the 5' carbon of the next sugar.
5. Note that the nitrogenous bases are attached to the sugars and are not part of the backbone itself, and that peptide bonds are not involved in DNA structure.