In the structure of DNA, what are the sides (backbone) of the DNA ladder composed of?

• A. Alternating sugar and phosphate groups
• B. Nitrogenous base pairs
• C. Fatty acid chains
• D. Amino acids

Answer: (A)

Verified step by step guidance

1. Recall the basic structure of DNA, which is often described as a double helix resembling a twisted ladder.
2. Identify the components of the DNA ladder: the 'rungs' are made of nitrogenous base pairs, while the 'sides' or backbone are made of repeating units.
3. Understand that the backbone consists of alternating sugar and phosphate groups linked together by phosphodiester bonds.
4. Recognize that nitrogenous bases (adenine, thymine, cytosine, guanine) attach to the sugar molecules but do not form the backbone itself.
5. Conclude that the sides (backbone) of the DNA ladder are composed of alternating sugar and phosphate groups.