Which components form the backbone of a DNA molecule?

• A. Nitrogenous bases and phosphate groups
• B. Phosphate and uracil
• C. Deoxyribose and adenine
• D. Alternating phosphate and deoxyribose groups

Answer: (D)

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 sugar.
2. Identify the sugar in DNA as deoxyribose, which alternates with phosphate groups to form the backbone.
3. Understand that nitrogenous bases (adenine, thymine, cytosine, guanine) are attached to the deoxyribose sugars but do not form the backbone itself.
4. Recognize that uracil is found in RNA, not DNA, so phosphate and uracil cannot form the DNA backbone.
5. Conclude that the backbone of DNA is formed by alternating phosphate groups and deoxyribose sugars.