CELL BIOLOGY A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site nucleolus The nucleolus is the dark circle within the larger mottled circle of the nucleus The site of ribosomal RNA (rRNA) synthesis in eukaryotic cells. The nucleolus is dense, spherical in shape, and made up principally of rRNA that is in the process of being transcribed from rRNA genes. It lies within the cell nucleus and is surrounded by the nuclear membrane. During cell division the nucleolus disappears. Related category    • CELL BIOLOGY Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP