Complementary Base Pairing in Transcription

Steps:

• Transcription synthesizes RNA complementary to the DNA template strand using hydrogen bonds in the transcription bubble.
• Base pairing rules: DNA C forms 3 hydrogen bonds with incoming RNA G nucleotide.
• Evaluate choices for matching DNA template base to RNA base.
• Choice B depicts C (DNA) _____ G (RNA), aligning with this rule.

Why B is correct:

• DNA cytosine pairs with RNA guanine via 3 temporary hydrogen bonds, per Watson-Crick rules adapted for DNA-RNA hybrid.

Why the others are wrong:

• A: DNA A pairs with RNA U via 2 hydrogen bonds, not matching the 3-bond C-G interaction emphasized in transcription diagrams.
• C: Shows G _____ C, which reverses the standard template (DNA G to RNA C) orientation for the depicted bonding.
• D: DNA T pairs with RNA A, not U; T-U forms no valid hydrogen bonds.

Final answer: B