The Cell Nucleus

The nucleus is the most prominent feature of a eukaryotic cell – cells that have nuclei. It is quite easy to recognize the nucleus when you look at a cell through microscope as it is an organelle that is enclosed by a membrane, forming a very distinct “center” in the cellular structure. The nucleus houses majority of the genetic material of the cell, particularly the molecules of DNA that are responsible for the control of the cell’s general activity, which in turn expresses the organism’s identity. It is the nucleus that maintains the expression of genes by managing the cell’s activities based on the genetic plan imprinted in the organism.

Components of the Nucleus

The nucleus is comprised of the nuclear envelope, the cytoskeleton, chromosomes, the nucleolus, and sub-nuclear bodies.

1. The Nuclear Envelope – this serves as the container that keeps materials within the nucleus, allowing just some items to pass through and from by means of little holes. The nuclear envelope is comprised of two cell membranes that act as parallel walls. The little holes are called nuclear pores and act as a regulatory system of the nucleus so that only water-soluble substances are allowed to enter and exit.

2. Cytoskeleton – this provides mechanical support in animal cells. The cytoskeleton is actually a web of intermediate filaments that both give the nuclear envelope structural support and the chromosomes anchoring sites. The cytoskeleton is made of nuclear lamina, which are comprised of proteins called lamins.

3. Chromosomes – these are structures that contains most of the genetic material of the cell in the form of several molecules of DNA. For majority of the cell’s cycle, chromosomes are organized in a complex of DNA-proteins known as chromatin but when the cell divides, the chromosomes become well defined and are seen as pairs of rods that line up to be split.

4. The Nucleolus – when you look closely at a nucleus, you might observe a dense structure that seems to be a “nucleus” of the nucleus. This is the a concentration of genetic material. However, the nucleolus is not enveloped by a membrane like the nucleus. It is where several strands of DNA, rDNA, and RNA congregate.

5. Subnuclear bodies – there are other distinct components of the nucleus that, like the nucleolus, are not delineated by a membrane. These include the Cajal bodies or gems, PTF and PIKA domains, promyelocytic leukaemia bodies, paraspeckles, splicing speckles. These subnuclear bodies contribute to the genetic function of the nucleus.