What are the three parts of a nucleotide?

• A. Phosphate group, deoxyribose sugar, nitrogen base
• B. Amino group, ribose sugar, nitrogen base
• C. Phosphate group, ribose sugar, lipid base
• D. Phosphate, deoxyribose, amino acid

Answer: (A)

Nucleotides—the building blocks of DNA and RNA—have three parts: a phosphate group, a sugar, and a nitrogenous base. In DNA the sugar is deoxyribose, which distinguishes DNA from RNA (which uses ribose). The phosphate group links the sugars of adjacent nucleotides through phosphodiester bonds, creating the backbone of the strand. The nitrogenous base sticks off the sugar and carries the genetic information through its sequence, pairing with a complementary base on the opposite strand. Other options include components that aren’t part of nucleotides (like an amino group from amino acids) or use a sugar that isn’t correct for DNA (ribose). So the correct trio is phosphate group, deoxyribose sugar, and nitrogenous base.