The Nucleus

The nucleus isolates DNA, which contains the code for protein assembly, from the sites (ribosomes in cytoplasm) where proteins will be assembled. The nucleus controls access to DNA and permits easier packing of DNA during cell division. Localization of the DNA makes it easier to sort out hereditary instructions when the time comes for a cell to divide. The membranous boundary of the nucleus helps control the exchange of signals and substances between the nucleus and the cytoplasm.

The nuclear envelope surrounding the nucleus consists of two lipid bilayers with pores. It surrounds the nucleoplasm within. On the inner surface are attachment sites for protein filaments that anchor the DNA molecules and keep them organized.

The nucleolus is located within the nucleus. The nucleolus appears as a darker globular mass. It is a region where subunits of ribosomes are prefabricated before shipment out of the nucleus.

Chromatin refers to the cell's total collection of DNA and associated proteins. A chromosome is an individual DNA molecule and its associated proteins. DNA is duplicated and condensed before cell division occurs.

REVIEW: An organelle found in the nucleus is a

REVIEW: Scientists use the word "chromosome" to describe

PREVIOUS

NEXT

LECTURE 4 INDEX

MAIN INDEX