Which component forms the backbone of the DNA molecule?

• A. Amino acids
• B. Nitrogenous bases
• C. Hydrogen bonds
• D. Alternating sugar and phosphate groups

Answer: (D)

Verified step by step guidance

1. Recall the structure of a DNA molecule, which consists of three main components: nitrogenous bases, sugar molecules, and phosphate groups.
2. Understand that the nitrogenous bases (adenine, thymine, cytosine, guanine) pair up through hydrogen bonds to form the rungs of the DNA ladder.
3. Recognize that the sugar and phosphate groups alternate to form the sides of the DNA ladder, creating a repeating sugar-phosphate backbone.
4. Note that amino acids are not part of the DNA structure; they are the building blocks of proteins.
5. Conclude that the backbone of DNA is formed by alternating sugar and phosphate groups linked together by covalent bonds.