Given a scientific passage and an answer, generate a question for the given answer.

Input: Consider Input: Passage: Plasma cells are activated B cells that secrete antibodies. Antibodies are large, Y-shaped proteins that recognize and bind to antigens. Plasma cells are like antibody factories, producing many copies of a single type of antibody. The antibodies travel throughout the body in blood and lymph. Each antibody binds to just one kind of antigen. When it does, it forms an antigen-antibody complex (see Figure below ). The complex flags the antigen-bearing cell for destruction by phagocytosis . Answer: antibodies

Output: What do you call large, y-shaped proteins that recognize and bind to antigens?

Input: Consider Input: 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

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

Input: Consider Input: Passage: The midpiece of the sperm is packed with mitochondria. Mitochondria are organelles in cells that produce energy. Sperm use the energy in the midpiece to move. Answer: mitochondria
Output: What is the midpiece of sperm packed with?