Which base pairing is correct in DNA?

Which base pairing is correct in DNA?

• A. Adenine pairs with thymine; cytosine pairs with guanine
• B. Adenine–Cytosine
• C. Guanine–Uracil
• D. Thymine–Guanine

Answer: (A)

DNA base pairing follows specific complementary rules. In DNA, adenine pairs with thymine and cytosine pairs with guanine. These pairings are stabilized by hydrogen bonds (two between A and T, three between G and C), which helps maintain a uniform double-helix width and enables accurate replication. This is supported by Chargaff’s rules, which state that A pairs with T and G pairs with C in double-stranded DNA. Uracil occurs in RNA, not DNA, so pairing guanine with uracil is not correct for DNA. Similarly, pairing adenine with cytosine or thymine with guanine would disrupt the proper, complementary structure.

DNA base pairing follows specific complementary rules. In DNA, adenine pairs with thymine and cytosine pairs with guanine. These pairings are stabilized by hydrogen bonds (two between A and T, three between G and C), which helps maintain a uniform double-helix width and enables accurate replication. This is supported by Chargaff’s rules, which state that A pairs with T and G pairs with C in double-stranded DNA. Uracil occurs in RNA, not DNA, so pairing guanine with uracil is not correct for DNA. Similarly, pairing adenine with cytosine or thymine with guanine would disrupt the proper, complementary structure.