The nucleus and ribosomes relationship is:

• A. The nucleus transcribes DNA into mRNA, which is translated by ribosomes to build proteins.
• B. Ribosomes transcribe DNA into mRNA.
• C. The nucleus translates mRNA into proteins.
• D. Mitochondria produce ribosomes for protein synthesis.

Answer: (A)

The main idea tested here is the flow of genetic information: transcription in the nucleus followed by translation at the ribosomes to make proteins. In the nucleus, DNA is transcribed into messenger RNA by RNA polymerase. This mRNA then travels to the cytoplasm, where ribosomes read its codons and assemble amino acids into a polypeptide, which folds into a functional protein. That’s why this option correctly links the nucleus to ribosomes: transcription happens in the nucleus, translation happens at the ribosomes.

Ribosomes don’t transcribe DNA, so statements claiming transcription occurs there are wrong. Likewise, translation isn’t done in the nucleus, so saying the nucleus translates mRNA into proteins isn’t accurate. Mitochondria have their own ribosomes for some mitochondrial proteins, but they aren’t the site of cytosolic protein synthesis for the cell as a whole, so that claim is misleading for the general process.