In DNA structure, what molecules make up the repeating backbone of a DNA strand?

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

Answer: (A)

Verified step by step guidance

1. Understand the structure of a DNA strand, which consists of a backbone and nitrogenous bases attached to it.
2. Recall that the backbone of DNA is made up of sugar and phosphate molecules linked together.
3. Identify the specific sugar in DNA as deoxyribose, which differs from ribose found in RNA.
4. Recognize that the sugar and phosphate groups alternate to form the repeating backbone structure.
5. Conclude that the repeating backbone of a DNA strand is composed of alternating deoxyribose sugars and phosphate groups.