Which organelle contains the genetic material and directs all cell activities?

• A. Ribosome
• B. Chloroplast
• C. Golgi
• D. Nucleus

Answer: (D)

The main idea is that the nucleus acts as the cell’s control center. It stores the cell’s genetic material in DNA, which holds the instructions for making every molecule the cell needs. By transcription of DNA into RNA, the nucleus regulates which proteins are produced, guiding growth, responses to signals, and all the activities a cell carries out. The nucleus is also surrounded by a nuclear envelope with pores that control what enters and leaves, and it contains the nucleolus where ribosomes begin to form. While other organelles have important jobs—ribosomes build proteins, chloroplasts (in plants) carry out photosynthesis and contain some DNA, and the Golgi packages and ships proteins—they do not direct the entire set of cellular activities the way the nucleus does.