Where does transcription occur in eukaryotic cells?

• A. In the cytoplasm
• B. In the ribosome
• C. In the mitochondria
• D. In the nucleus

Answer: (D)

Transcription in eukaryotic cells happens in the nucleus because that's where the DNA is stored and where RNA processing takes place. The enzyme RNA polymerase reads the DNA template in the nucleus to synthesize a primary RNA transcript. Before this RNA can be used to make a protein, it must be processed—capped, spliced, and polyadenylated—in the nucleus, and then the mature mRNA is exported through nuclear pores to the cytoplasm. In the cytoplasm, ribosomes carry out translation, not transcription. There is transcription in mitochondria as well, since mitochondrial DNA has its own genes, but for the cell’s main gene expression, the nucleus is the key site.