Which base-pairing rule is used in DNA replication?

Which base-pairing rule is used in DNA replication?

• A. A pairs with T and G pairs with C
• B. A pairs with C and G pairs with T
• C. A pairs with U
• D. C pairs with G and A pairs with T

Answer: (A)

During DNA replication, the genetic information is preserved by complementary base pairing: adenine pairs with thymine, and guanine pairs with cytosine. As the double helix unwinds, each strand serves as a template for a new strand. DNA polymerase adds nucleotides opposite the template bases so that A on the template strand pairs with T on the new strand and G pairs with C. This ensures the two new DNA molecules are exact copies of the original. A–T pairing forms two hydrogen bonds, while G–C pairing forms three, contributing to the stability of the DNA duplex. In DNA, thymine is used rather than uracil, which is present in RNA, so A pairs with U in RNA contexts but not in DNA replication.

During DNA replication, the genetic information is preserved by complementary base pairing: adenine pairs with thymine, and guanine pairs with cytosine. As the double helix unwinds, each strand serves as a template for a new strand. DNA polymerase adds nucleotides opposite the template bases so that A on the template strand pairs with T on the new strand and G pairs with C. This ensures the two new DNA molecules are exact copies of the original.

A–T pairing forms two hydrogen bonds, while G–C pairing forms three, contributing to the stability of the DNA duplex. In DNA, thymine is used rather than uracil, which is present in RNA, so A pairs with U in RNA contexts but not in DNA replication.