DNA's backbone is formed by which components?

DNA's backbone is formed by which components?

• A. Sugar-phosphate
• B. Nitrogenous bases
• C. Proteins
• D. Lipids

Answer: (A)

The critical idea is that the DNA backbone is the sugar-phosphate chain that provides the structural framework of the molecule. Each nucleotide contributes a deoxyribose sugar and a phosphate group, and phosphodiester bonds link the 3' carbon of one sugar to the 5' carbon of the next, creating a repeating sugar-phosphate backbone with clear 5' to 3' directionality. The nitrogenous bases attach to the 1' carbon of the sugar and extend inward, where bases from two strands pair to form the double helix. Lipids and proteins are not part of this backbone, though proteins can interact with DNA in chromatin.

The critical idea is that the DNA backbone is the sugar-phosphate chain that provides the structural framework of the molecule. Each nucleotide contributes a deoxyribose sugar and a phosphate group, and phosphodiester bonds link the 3' carbon of one sugar to the 5' carbon of the next, creating a repeating sugar-phosphate backbone with clear 5' to 3' directionality. The nitrogenous bases attach to the 1' carbon of the sugar and extend inward, where bases from two strands pair to form the double helix. Lipids and proteins are not part of this backbone, though proteins can interact with DNA in chromatin.