Which DNA base pairing is correct in a standard double-stranded DNA molecule?

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

Answer: (A)

Verified step by step guidance

1. Recall that DNA is composed of four nitrogenous bases: adenine (A), thymine (T), guanine (G), and cytosine (C).
2. Understand that base pairing in DNA follows Chargaff's rules, where adenine pairs specifically with thymine, and guanine pairs specifically with cytosine.
3. Recognize that adenine (A) pairs with thymine (T) through two hydrogen bonds, while guanine (G) pairs with cytosine (C) through three hydrogen bonds, ensuring stability and specificity.
4. Note that uracil (U) is found in RNA, not DNA, so A does not pair with U in DNA molecules.
5. Conclude that the correct base pairing in standard double-stranded DNA is A pairs with T, and G pairs with C.