Which statement about the phosphate group in DNA is true?

Which statement about the phosphate group in DNA is true?

• A. Phosphate is attached to the base.
• B. Phosphate forms the bond between the base pairs.
• C. Phosphate is attached to the sugar to form the backbone of the molecule.
• D. Phosphate is only present during replication.

Answer: (C)

The phosphate group is part of the sugar–phosphate backbone of DNA. Each nucleotide has a sugar (deoxyribose), a phosphate, and a base. The backbone is formed when the phosphate of one nucleotide bonds to the sugar of the next nucleotide, creating phosphodiester linkages that run along the length of the strand (from the 5′ phosphate of one sugar to the 3′ hydroxyl of the next). The bases themselves project outward from this backbone and pair with complementary bases on the opposite strand via hydrogen bonds. So the phosphate group’s role is to connect sugars and build the backbone, not to attach to the bases or to form the bonds between base pairs. Phosphate is a permanent part of DNA, present irrespective of replication.

The phosphate group is part of the sugar–phosphate backbone of DNA. Each nucleotide has a sugar (deoxyribose), a phosphate, and a base. The backbone is formed when the phosphate of one nucleotide bonds to the sugar of the next nucleotide, creating phosphodiester linkages that run along the length of the strand (from the 5′ phosphate of one sugar to the 3′ hydroxyl of the next). The bases themselves project outward from this backbone and pair with complementary bases on the opposite strand via hydrogen bonds. So the phosphate group’s role is to connect sugars and build the backbone, not to attach to the bases or to form the bonds between base pairs. Phosphate is a permanent part of DNA, present irrespective of replication.