Introduction
The nucleus is the largest organelle of a cell and is located in the cytoplasm of eukaryotic cells. The round cell nucleus, which is bounded by a double membrane (nuclear envelope), contains the genetic information packed in chromatin, the deoxyribonucleic acid (DNA). As a store of genetic information, the cell nucleus plays a central role in heredity.
Function of the cell nucleus
All human cells except erythrocytes have a cell nucleus in which DNA is present in the form of chromosomes. The cell nucleus regulates and controls all processes that take place in a cell. For example, the instructions for the synthesis of proteins, the transmission of genetic information, cell division and various metabolic processes.
In addition to the storage of genetic information, the duplication (replication) of DNA and the synthesis of ribonucleic acids (RNA) by rewriting DNA (transcription), as well as the modification of this RNA (processing) are among the most important functions of the cell nucleus. In addition to the DNA in the cell nucleus, humans also possess mitochondrial DNA in the mitochondria, whose replication is completely independent of the nucleus. The information of many proteins, which are necessary for the respiratory chain, is stored here.
What is the nucleus substance?
The cell nucleus substance is the genetic information encoded in the cell nucleus. This is also known as DNA (deoxyribonucleic acid). A molecule of DNA or RNA is in turn made up of basic chemical building blocks, the nucleotides, and consists of a sugar (deoxyribose for DNA or ribose for RNA), an acid phosphate residue and a base.
The bases are called adenine, cytosine, guanine or thymine (or uracil for RNA). The DNA is unique because of the fixed sequence of the four bases, which is different in each person. The DNA is not present as a free strand, but is wrapped around special proteins (histones), which together are called chromatin.
If this chromatin is further compressed, the chromosomes are ultimately formed, which become visible under the microscope in the metaphase of mitosis. The rod-shaped corpuscles are thus the carriers of genetic information and are involved in cell division. A normal human somatic cell has 46 chromosomes arranged in pairs (double or diploid set of chromosomes).
23 chromosomes come from the mother and 23 chromosomes from the father. In addition, the nucleus contains the nucleolus, which is particularly conspicuous as a condensed zone. It consists of ribosomal RNA (rRNA).
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