The internationally recognised abbreviation for the English term deoxyribonucleic acid is DNA. This is made up of "de-oxy" (without oxygen), "ribo" (sugar type ribose) and "nucleic acid" (nucleic acid). The term DNA (deoxyribonucleic acid), which was previously used in German-speaking countries, is rarely used today to avoid confusion with the Domain Name System (also DNS) of the Internet.

Decoding DNA

The structure of DNA was discovered in 1953 by biologists James Watson (1928-2025) and Francis Crick (1916-2004). Together with Maurice Wilkins (1916-2004), they were awarded the Nobel Prize for Medicine in 1962.

The first decoding of human DNA took place between 1990 and 2003 as part of the Human Genome Project (HGP). However, a complete sequence has only been available since 2022, after areas that were previously difficult to access, such as centromeres and telomeres, were decoded using new technologies.

Humans & grapevines

Around 98 to 99% of human DNA matches that of chimpanzees and around 99.9% matches that of other humans. The genetic difference between chimpanzees and orangutans is greater than that between chimpanzees and humans. A European and a black African can be genetically more similar than two Europeans (e.g. a Sicilian and a Norwegian). Skin colour is only an insignificant detail. Therefore, the term "race", which is no longer relevant in science, is obsolete. This also applies to the berry colour of grape varieties, which is not a species characteristic. Pinot Noir, Pinot Gris and Pinot Blanc are, strictly speaking, one variety (see under Pinot).

Around half of the genes in the human genome (see below) have functional equivalents in animals and plants, although the corresponding DNA sequences are not identical. Many basic cell processes such as metabolism, cell division, DNA repair and protein biosynthesis are very similar in humans, animals and plants. The percentages in the graph are based on comparisons of selected DNA markers; however, similarity does not mean identical. In plants, the percentage of functionally similar genes is meant.

Structure of DNA

DNA consists of three basic chemical building blocks. These are deoxyribose (a derivative of the sugar ribose, which consists of five carbon atoms ), phosphoric acid and four organic bases, which together form nucleic acid. It is a chain molecule that occurs in the cell nuclei of all plant, fungal and animal organisms, including humans. As a carrier of genetic information, it serves as a blueprint, so to speak, for controlling and maintaining all biological life processes and is inherited from the parents.

Size & storage location

The length of DNA is just under two metres. However, it is not a single continuous strand, as DNA is divided into individual, clearly demarcated chromosomes. As a human being consists of around 100 trillion cells, this results in a total length of the DNA it contains of around 150 billion kilometres. This corresponds to around a thousand times the distance from the earth to the sun at 150 million kilometres. In each individual cell, the entire DNA is located in the cell nucleus. In plants, the cell nucleus is shown as No. 5 in the diagram below.

Double helix

The individual DNA sections are structured in a helically twisted form, also known as a double helix (hélix = winding). This can be visualised as an extremely long, thin rope ladder. This structure forms the basis of all chromosomes in a spiral and highly condensed form, in which the genetic information is stored. The diagram shows a very small section of a DNA strand with relatively few genes.

Base pairs

The two sides or rods of the ladder (strands) consist of phosphate and sugar molecules(deoxyribose) to which the four bases adenine, guanine, cytosine and thymine are attached. Two opposite bases are called base pairs. A base pair is the smallest unit of information in DNA. The connection of the pairs is the "rung" of the ladder, whereby there are only two different pairs that fit together like a lock and key: A and T form one pair, and C and G form the other. If the molecules on one strand result in a DNA section "TAACGCCCTTA", then this results in the sequence "ATTGGCGGGAAT" on the opposite strand.

The "DNA ladder" is also known as the "gene alphabet", whereby the sequence of the base pairs plays an important role. The genetic code is read (decoded) by the cell and the proteins are built on the basis of the information it contains. The proteins consist of amino acids that are linked together in a precisely defined sequence. The individual proteins each have specific tasks. The sequence of base pairs determines how proteins are composed and how the organism is organised in all its details.

Nucleotides

A phosphate group and a sugar unit form the backbone of a molecule (part of the blue band). Together with a base, these form a nucleotide (red ellipses). Many such nucleotides combine to form a macromolecule of DNA. In addition to their function as information storage, nucleic acids, which are considered the "key molecules of life", can also serve as signal transmitters or catalyse (initiate) biochemical reactions.

Genes

A gene is the general term for a tiny section of the DNA chain. Each gene is responsible for certain functions in an organism, either alone (monogenic) or in combination with others (polygenic). These are, for example, eye colour, blood group or character traits in humans as well as flower formation, berry colour, growth height, leaf shape or ripening time in grapevines.

In addition to the genetic make-up, the environment also plays an important role in the development of an organism. It is not clear whether genetics or environmental factors have the greater influence. In most cases there is an interaction - sometimes one predominates, sometimes the other, depending on the context and developmental phase.

RNA & mRNA

A gene contains the information for the formation of an RNA (ribonucleic acid) through the process of transcription (Latin transcribere = to transcribe). In this process, a single gene is transcribed from the DNA so that the cell can work with it. This creates an mRNA (messenger RNA). This is a type of copy of the gene that can leave the cell nucleus and travel to the cell's protein factory. A protein is then produced there according to this blueprint. In contrast to DNA, RNA is not present as a double helix, but only as a single strand. It contains the sugar ribose instead of deoxyribose and the base uracil instead of thymine (nucleic bases).

The task of RNA is to "read" the information stored in the DNA and then transport it to various locations within the cell. An essential function of RNA in the cell is the conversion of genetic information into proteins. When building a house, the blueprint could be described as DNA and the craftsmen working on it as RNA. Humans have around 25,500 genes, whereas the water flea has 30,000 and the West African lungfish as many as 40,000. So it is not the number of genes that matters, but their regulation, interconnection and the interactions between them.

Allele

An allele (gene variant) is the term for a specific variant of a gene (small DNA segment) that is found at a specific gene locus (location) of a chromosome. Alleles are responsible for many genetic characteristics, such as colour, growth, leaf shape, ripening time or disease resistance. Many so-called biomarkers are based on such allele differences. Alleles can be identical = homozygous or different = heterozygous. In diploid organisms, they are present in pairs, as each chromosome is present twice - one from the mother and one from the father (see the two keywords alleles and heterozygosity for more information on this phenomenon).

Cell

The cell is the smallest functional unit of all living organisms. It consists of many separate areas with different functions. The diagram shows the internal...