Final answer:
The "brain" of the cell which stores most of the DNA and produces ribosomes is the nucleus, where the nucleolus resides for ribosomal RNA synthesis.
Step-by-step explanation:
The "brain" of the cell which stores most DNA and produces ribosomes is the nucleus. The nucleus is typically the most prominent organelle in a cell, and it houses the cell's DNA and directs the synthesis of ribosomes and proteins. The nucleolus, which is located within the nucleus, is specifically the site where ribosomal RNA is synthesized and the first stages of ribosome assembly occur. DNA is found within the nucleus of animal cells, except for certain cells like red blood cells (RBCs) which do not contain nuclei. The endomembrane system, which includes the rough endoplasmic reticulum, is responsible for processing and shipping proteins specified by the nucleus.