Non-template strand in transcription

Steps:

• Recall that transcription uses the template strand to synthesize RNA, while the non-transcribed (coding) strand has the same sequence as the mRNA (with T instead of U).
• In diagrams, the template strand is shown being read 3' to 5' by RNA polymerase, with RNA growing 5' to 3'.
• Identify the strand not bound to or read by the polymerase as the non-transcribed one.
• Match diagram labels: the strand parallel but not antiparallel to emerging RNA indicates the coding strand.

Why A is correct:

• Option A depicts the strand matching mRNA sequence, defining it as the non-template (coding) strand per central dogma.

Why the others are wrong:

• B shows the template strand, as it's antiparallel and read by polymerase.
• C illustrates the RNA transcript, not a DNA strand.
• D labels the promoter region, unrelated to transcribed/non-transcribed strands.

Final answer: A