Nucleus where is it found

The shape of the nucleus is variable and is usually adapted to the morphology of the cell Figure 1. Typically, the nucleus is rounded, but other forms are also found, as in neutrophils, which contain multi-lobulated nucleus.

The location of the nucleus is normally in the center of the cell, but it can also be found in peripheral locations. For example, secretory cells have their nucleus situated in the basal part, and skeletal muscle cells have their nuclei close to the plasma membrane. A lthough the amount of DNA is almost the same in all the cell nuclei of an organism, the size of the nucleus is variable depending on the cell type Figure 2.

Furthermore, cells from species with different amount of DNA may show a similar nuclear size. These data indicate that the size of the nucleus is adapted to the size and the physiology of the cell, but does not depend closely on the amount of DNA.

A nucleus may contain up to four nucleoli, but within each species the number of nucleoli is fixed. After a cell divides, a nucleolus is formed when chromosomes are brought together into nucleolar organizing regions. During cell division, the nucleolus disappears. Some studies suggest that the nucleolus may be involved with cellular aging and, therefore, may affect the senescence of an organism.

The Nuclear Envelope - The nuclear envelope is a double-layered membrane that encloses the contents of the nucleus during most of the cell's lifecycle.

The space between the layers is called the perinuclear space and appears to connect with the rough endoplasmic reticulum. The envelope is perforated with tiny holes called nuclear pores. These pores regulate the passage of molecules between the nucleus and cytoplasm, permitting some to pass through the membrane, but not others.

The inner surface has a protein lining called the nuclear lamina, which binds to chromatin and other nuclear components. During mitosis, or cell division, the nuclear envelope disintegrates, but reforms as the two cells complete their formation and the chromatin begins to unravel and disperse. Nuclear Pores - The nuclear envelope is perforated with holes called nuclear pores.

Building blocks for building DNA and RNA are allowed into the nucleus as well as molecules that provide the energy for constructing genetic material. License Info. The chromosomes have been arranged into their pairs with their numbers are shown below.

The characteristic banding pattern you can see is obtained by staining with Giemsa. Have a look at the genome mapping project for humans and other species at the National Center for Biotechnology Information website. Cell death occurs due to necrosis - i. Cell nuclei also look different when the cells degenerate as shown here: The nucleus can look very dark and purple, and the cell has very little cytoplasm - pyknotic.

Alternatively, the nucleus can look very faded - karyolitic. What is the nucleus? This image below shows a diagram of the nucleus. The nucleus of a cell in interphase. An electron micrograph of a nucleus. Types of Nucleus Cells are normally diploid - this means that they have a pair - two sets of homologous chromosomes, and hence two copies of each gene or genetic locus. Its central location enables it to reach all parts of the cell easily. As RNA and proteins pass through the nuclear envelope, they can do so easily in part due to the neutral location of the nucleus.

Eukaryotic cells typically only have one nucleus. Nucleic Acid Facts. The Location of Ribosomes in a Cell.

Cell Characteristics.