Q.State the principal function of the nucleolus within the nucleus, in terms of what it is the site of.

A labelled diagram of the nucleus should show: nuclear envelope (outer & inner membrane + perinuclear space), nuclear pores, nucleoplasm, chromatin (euchromatin/heterochromatin), and the nucleolus.

Since this is a 'draw and label' question, here is the structure to be represented, part by part, exactly as it should appear in the labelled diagram:

1. Nuclear envelope: A double membrane (outer and inner) enclosing the nucleus, continuous with the endoplasmic reticulum, with a narrow perinuclear space between the two membranes.
2. Nuclear pores: Numerous pore complexes perforating the nuclear envelope at intervals, which regulate the movement of RNA and proteins between the nucleus and cytoplasm.
3. Nucleoplasm (karyolymph): The semi-fluid matrix filling the interior of the nucleus, in which the chromatin and nucleolus are suspended.
4. Chromatin: The DNA-protein complex, seen as a loosely coiled network; the more condensed, darkly staining regions are heterochromatin and the loosely packed, lightly staining regions are euchromatin. …