The structure of our genetic information
A healthy lifestyle includes sport, a balanced diet and a thoughtful approach to one’s own body. On a biological level, healthy and intact cells are the prerequisite for this. The human body consists of a large number of cells. Human cells have the ability to repair themselves even in the case of injuries, infections with pathogens and changes in genetic information. In addition, these cells can warn surrounding cells and send themselves into a controlled cell death. In maintaining and promoting viable and healthy cells, the intact genetics of each individual cell plays a particularly important role. Genetics represents the linchpin of every cell and is significantly involved in the development of disease. But what is our genetic information and how is it actually structured?
Our facts-to-go briefly and concisely summarized for you !
- With a few exceptions (e.g. erythrocytes), all human cells have a nucleus with 46 linear chromosomes. Each chromosome is present in duplicate, one inherited from the mother and the other from the father.
- If one speaks of the human genome, this term includes the totality of all chromosomes and furthermore also the mtDNA.
- Chromosomes consist of DNA. The detailed structure of DNA consists of several nucleotides strung together. These molecules consist of a sugar, a phosphate residue and one of four bases (cytosine, thymine, adenine, guanine). Two “nucleotide chains” are always opposite each other and form a double helix.
- The sequence of the individual bases determines the genetic code and the individual composition of a genome.
- Genes are sections on the DNA that represent a coding unit of a specific protein. This means that this section on the DNA is used to form a protein.
Our genome is composed of the totality of chromosomes
Every cell in our body, with a few exceptions such as erythrocytes, has a nucleus containing hereditary information, which is made up of thread-like (linear) DNA molecules. These molecules are called chromosomes. The term genome encompasses the totality of an organism’s genetic information — that is, all of those chromosomes found in every cell.
Each cell has 46 chromosomes (DNA molecules).
Human cells are equipped with a general set of chromosomes. This means that each cell of an individual always has the same chromosomes and thus the same genetic information. In total, 23 chromosomes are distinguished in each cell nucleus. However, each chromosome is present in duplicate. Consequently, 46 chromosomes are found in each cell, 23 of which are inherited from the mother and 23 from the father.
A genome is unique
Chromosomes 1 to 23 differ within an individual not only in structure but also in size. Not to mention that the chromosomes of all individuals differ considerably in molecular structure. The individual structure and unique composition of specific chromosomes represent the genetic fingerprint of each individual. Each of us has our own genome, which is not found in this form in any other living being.
Chromosomes consist of DNA, which is composed of nucleotides.
More precisely, the carrier of genetic information is not the chromosome itself, but DNA. This abbreviation stands for the term “deoxyribonucleid acid”. This DNA is composed of so-called nucleotides. They are the building blocks of genetic information and consist of a purine or pyrimidine base (cytosine, thymine, adenine, guanine), a sugar and a phosphate residue. Strictly speaking, nucleotides strung together represent our genetics. Simplified, the individual nucleotides differ only in the different base, of which there are four.
The resulting chains are always in pairs. This means that two such sequences of nucleotides are opposite each other. The bases are directed towards the center and connect via hydrogen bonds. This is also known as the double helix. The bases adenine and thymine and cytosine and guanine always pair up.
The genetic code is determined by the sequence of bases
Sequencing or “decoding” the genetic code means finding out the sequence of bases. If you string together thousands of nucleotides that differ only in the base, the sequence of bases determines the individual composition of a genome. And it is precisely this sequence of bases that holds the key to many acquired and congenital diseases. A wide variety of internal and external influences can lead to a change in the sequence of bases and, as a consequence, to incorrect genetic information.
Certain regions of the nucleotides strung together form genes
The nucleotides that follow one another represent the functional units of genetics. Individual and also groups of nucleotides pursue a wide variety of tasks. Knowledge about our genes plays the most important role in understanding our genetic information as a whole. Genes are sections on the DNA (i.e. sequences of nucleotides) that represent a coding unit of a specific protein. This means that this section on the DNA is used to form a protein (more on this in the next article on genetics).
Mitochondria also possess genetic information
However, the totality of our genetic information is not only found in the nucleus of each individual cell. The “power plants” of our cells also have their own DNA. These so-called mitochondria belong to the organelles of human cells. Organelles are virtually the organs of a cell. Mitochondria play an important role in our body and serve in particular to produce energy. The DNA found there also consists of nucleotides, which are connected by two opposite chains. However, these chains do not form a linear chromosome, but a ring-shaped store of genes. The genetic information of the mitochondria (mtDNA) differs in detail from the genetic information of our cell nuclei. Primarily, it is used to produce proteins that the mitochondrion itself needs. Strictly speaking, this DNA must consequently also be assigned to the human genome. The mtDNA is always inherited from the mother. Hereditary diseases affecting the mtDNA therefore usually originate from the mother.
Text-Sources:
(1) Nordheim und Knippers, Molekulare Genetik, 11. Auflage, 2018
(2) Munk, Genetik, 2. Auflage, 2017
(3) Ulfig, Histologie, 5. Auflage, 2019
Image-Sources:
