A2 Genetic Control of Proteins and Control of Gene Expression Practice Test

In eukaryotic cells, translation happens on ribosomes that operate in the cytoplasm. After mRNA is made in the nucleus, it is exported to the cytoplasm where ribosomes—either free in the cytosol or attached to the rough endoplasmic reticulum—read the sequence and assemble amino acids into a polypeptide. The nucleus is where transcription occurs, so it isn’t the site of translation. While mitochondria (and chloroplasts in plants/algae) have their own ribosomes and can translate some of their own proteins inside those organelles, the majority of translation for cellular proteins happens in the cytoplasm. That’s why cytoplasm is the best answer.