What is the chemical backbone of DNA and which bases pair with which?

What is the chemical backbone of DNA and which bases pair with which?

• A. The backbone is ribose-phosphate; A pairs with T via two hydrogen bonds; G pairs with C via three hydrogen bonds.
• B. The backbone is deoxyribose-phosphate; A pairs with T via two hydrogen bonds; G pairs with C via three hydrogen bonds.
• C. The backbone is deoxyribose-phosphate; A pairs with C via hydrogen bonds; G pairs with T via three bonds.
• D. The backbone is ribose-phosphate; A pairs with C via two bonds; G pairs with T via three bonds.

Answer: (B)

DNA's backbone is built from deoxyribose sugar linked to phosphate groups, forming the deoxyribose-phosphate backbone. The bases pair specifically: adenine pairs with thymine using two hydrogen bonds, and guanine pairs with cytosine using three hydrogen bonds. This complementary pairing keeps the two DNA strands uniform in width and supports accurate replication, since each strand can serve as a template for the other. The other options mix in RNA-style ribose instead of deoxyribose or propose incorrect base pairings, which do not reflect how DNA actually pairs.

DNA's backbone is built from deoxyribose sugar linked to phosphate groups, forming the deoxyribose-phosphate backbone. The bases pair specifically: adenine pairs with thymine using two hydrogen bonds, and guanine pairs with cytosine using three hydrogen bonds. This complementary pairing keeps the two DNA strands uniform in width and supports accurate replication, since each strand can serve as a template for the other. The other options mix in RNA-style ribose instead of deoxyribose or propose incorrect base pairings, which do not reflect how DNA actually pairs.