Which statement describes Chargaff's base-pairing rule?

Which statement describes Chargaff's base-pairing rule?

• A. A=C and T=G
• B. A=T and C=G
• C. A=T and C=A
• D. A=G and C=T

Answer: (B)

DNA base pairing is highly specific: adenine pairs with thymine, and cytosine pairs with guanine. Chargaff’s rules show that in any double-stranded DNA, the amount of A equals T and the amount of C equals G. So the statement that A pairs with T and C pairs with G directly reflects both the pairing rules and the equal-base composition observed in both strands. If you tried to pair A with C or A with G, or claimed that A equals C or T equals G, you’d break the actual complementary pairing pattern and the equalities that Chargaff reported. This complementary pairing is what lets each strand serve as a template for the other during replication.

DNA base pairing is highly specific: adenine pairs with thymine, and cytosine pairs with guanine. Chargaff’s rules show that in any double-stranded DNA, the amount of A equals T and the amount of C equals G. So the statement that A pairs with T and C pairs with G directly reflects both the pairing rules and the equal-base composition observed in both strands. If you tried to pair A with C or A with G, or claimed that A equals C or T equals G, you’d break the actual complementary pairing pattern and the equalities that Chargaff reported. This complementary pairing is what lets each strand serve as a template for the other during replication.