Where do transcription and translation occur?

Where do transcription and translation occur?

• A. Transcription in the nucleus; translation at the ribosome in the cytoplasm
• B. Transcription in the cytoplasm; translation in the nucleus
• C. Both transcription and translation in the cytoplasm
• D. Both transcription and translation in the nucleus

Answer: (A)

In cells with a nucleus, the process that copies DNA into RNA happens inside the nucleus, while building proteins from that RNA happens outside the nucleus in the cytoplasm. DNA stays in the nucleus, and RNA polymerase makes the mRNA there. After the mRNA is processed, it exits to the cytoplasm where ribosomes read it and translate it into a protein. Ribosomes can be free in the cytoplasm or attached to the rough endoplasmic reticulum, but in either case translation occurs outside the nucleus. This separation by the nuclear envelope explains why transcription is in the nucleus and translation is in the cytoplasm. (In bacteria, which lack a nucleus, transcription and translation can occur in the same space, but that's a different cellular context.)

In cells with a nucleus, the process that copies DNA into RNA happens inside the nucleus, while building proteins from that RNA happens outside the nucleus in the cytoplasm. DNA stays in the nucleus, and RNA polymerase makes the mRNA there. After the mRNA is processed, it exits to the cytoplasm where ribosomes read it and translate it into a protein. Ribosomes can be free in the cytoplasm or attached to the rough endoplasmic reticulum, but in either case translation occurs outside the nucleus. This separation by the nuclear envelope explains why transcription is in the nucleus and translation is in the cytoplasm. (In bacteria, which lack a nucleus, transcription and translation can occur in the same space, but that's a different cellular context.)