In the DNA double helix, which two molecules form the repeating sugar-phosphate backbone of each strand?

• A. Deoxyribose sugar and phosphate group
• B. Deoxyribose sugar and nitrogenous bases
• C. Ribose sugar and phosphate group
• D. Nitrogenous bases and phosphate group

Answer: (A)

Verified step by step guidance

1. Understand the structure of DNA: DNA is composed of two strands forming a double helix, where each strand has a backbone and attached bases.
2. Identify the components of the backbone: The backbone of each DNA strand is made up of alternating sugar and phosphate groups.
3. Recall the specific sugar in DNA: The sugar in DNA is deoxyribose, which differs from ribose found in RNA.
4. Recognize that nitrogenous bases are not part of the backbone but are attached to the sugar molecules and pair between strands.
5. Conclude that the repeating sugar-phosphate backbone in DNA consists of deoxyribose sugar and phosphate groups.