What is the fundamental difference between transcription and translation in bacteria, and which enzymes drive each process?

• A. Transcription copies RNA into DNA via RNA polymerase; translation converts DNA into a protein.
• B. Transcription copies DNA into RNA via RNA polymerase; translation converts mRNA into a polypeptide on ribosomes using tRNAs.
• C. Transcription copies DNA into RNA via DNA polymerase; translation converts mRNA into a polypeptide.
• D. Transcription occurs in the nucleus and translation occurs in the cytoplasm.

Answer: (B)

In bacteria, transcription and translation are two steps of gene expression that operate in sequence but use different molecular machines. Transcription copies the genetic code from DNA into RNA, carried out by RNA polymerase. Translation then reads that RNA and assembles a protein on the ribosome, with transfer RNAs bringing the correct amino acids to match each codon.

RNA polymerase is the enzyme that drives transcription, making an RNA strand from the DNA template. For translation, the ribosome acts as the key catalytic machine to build the polypeptide, using tRNAs to deliver amino acids in the order specified by the mRNA. (Aminoacyl-tRNA synthetases help charge tRNAs with their correct amino acids.)

The other statements misstate the direction of synthesis or the enzymes involved (for example, RNA being copied into DNA, or DNA polymerase driving transcription), and in bacteria there’s no nucleus to separate transcription from translation, so both processes occur in the cytoplasm.