Which statement correctly summarizes Chargaff's rule?

Which statement correctly summarizes Chargaff's rule?

• A. A equals C and T equals G
• B. A equals G and C equals T
• C. A equals T and C equals G
• D. Base pairs are random

Answer: (C)

Chargaff's rule states that in double-stranded DNA, the amount of adenine equals thymine and the amount of cytosine equals guanine. This happens because adenine pairs with thymine and cytosine pairs with guanine, so their numbers balance across the two strands. Therefore, the statement that A equals T and C equals G is the correct summary. The other options would imply nonstandard or random base pairing, which would disrupt the consistent pairing that maintains the DNA double helix structure.

Chargaff's rule states that in double-stranded DNA, the amount of adenine equals thymine and the amount of cytosine equals guanine. This happens because adenine pairs with thymine and cytosine pairs with guanine, so their numbers balance across the two strands.

Therefore, the statement that A equals T and C equals G is the correct summary. The other options would imply nonstandard or random base pairing, which would disrupt the consistent pairing that maintains the DNA double helix structure.