Given a scientific passage and an answer, generate a question for the given answer.
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Question: Passage: Identify evidence for electroweak unification. The quarks in a particle are confined, meaning individual quarks cannot be directly observed. Are gluons confined as well? Explain. Answer: directly observed

Answer: The quarks in a particle are confined, meaning individual quarks cannot be what?

Question: Passage: Although most of a cell's DNA is contained in the cell nucleus, mitochondria have their own DNA. Mitochondria also have the machinery to manufacture their own RNAs and proteins. The human mitochondrial DNA sequence has 16,569 base pairs encoding 37 total genes: 22 tRNA genes, 2 rRNA genes, and 13 peptide genes. The 13 mitochondrial peptides in humans are integrated into the inner mitochondrial membrane, along with proteins encoded by nuclear genes. Answer: nucleus

Answer: Where is most of the cell's dna contained?

Question: Passage: Around 1850, a German doctor named Rudolf Virchow was observing living cells under a microscope. As he was watching, one of the cells happened to divide. Figure below shows a cell dividing, like the cell observed by Virchow. This was an "aha" moment for Virchow. He realized that living cells produce new cells by dividing. This was evidence that cells arise from other cells. Answer: cell division

Answer:
German doctor rudolf virchow first discovered what process when studying living cells under a microscope?