Which components form the backbone of the DNA molecule?

• A. Nitrogenous bases and phosphate groups
• B. Phosphate groups and ribose sugars
• C. Alternating deoxyribose sugars and phosphate groups
• D. Deoxyribose sugars and nitrogenous bases

Answer: (C)

Verified step by step guidance

1. Recall the structure of a DNA molecule, which consists of a sugar-phosphate backbone and nitrogenous bases attached to the sugars.
2. Identify the sugar present in DNA, which is deoxyribose, a five-carbon sugar lacking one oxygen atom compared to ribose in RNA.
3. Understand that the backbone of DNA is formed by alternating units of deoxyribose sugars and phosphate groups connected by phosphodiester bonds.
4. Recognize that nitrogenous bases (adenine, thymine, cytosine, guanine) are attached to the deoxyribose sugars but do not form the backbone itself.
5. Conclude that the correct components forming the DNA backbone are the alternating deoxyribose sugars and phosphate groups.