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DNA

Common international abbreviation for the English term deoxyribonucleic acid. The German term DNS (deoxyribonucleic acid) is hardly used any more to avoid confusion with the Domain Name System (DNS) of the Internet. The structure of DNA was discovered in 1953 by biologists James Watson (*1928) and Francis Crick (1916-2004), who together with Maurice Wilkins (1916-2004) were awarded the Nobel Prize for Medicine in 1962.

The name is derived from the first letters of the basic DNA building blocks deoxyribose (a type of sugar consisting of five carbon atoms) and type of sugara pentose), phosphoric acid and four bases, which make up nucleic acid. DNA is a chain molecule in the cell nuclei of all plant, fungal, animal and human organisms, which serves as a carrier of genetic information for the maintenance of all biological life processes and is inherited. The genes are responsible for every single function in an organism, such as cell division or metabolism.

The entire genetic material is called the genome, whereas a gene is a small section in the DNA chain of varying size. Each gene is responsible for certain functions by means of different proteins. For example, the OCA2 gene is responsible for almost all human eye colours. The genome contains the information for the production of RNA (ribonucleic acid = ribonucleic acid RNA). In contrast to DNA, RNA is not in the form of a double helixbut as a single strand. The task of RNA is to "read" the information stored in the DNA and convert it into proteins. In house building, the building plan can be described as DNA and the craftsmen working on it as RNA.

DNA - Doppel-Helix

Structure of DNA

The genes form a long chain molecule, which is made up of two single strands of DNA running in opposite directions in the form of a twisted rope ladder, also known as a double helix (hélix = winding). These are known as chromosomes (colour bodies). This can be imagined as an extremely long, thin rope ladder. The length of DNA in a human cell is almost two metres (see diagram at the bottom). As a human being consists of around 100 trillion of the body's own cells (25% of which are blood cells, which have no cell nucleus), the total length of DNA in a human being is 150 billion kilometres, which is around a thousand times the distance from the earth to the sun at around 150 million kilometres.

The two sides of the ladder (the rods) are called "strands". These consist of phosphoric acid and sugar molecules (deoxyribose), which are the four bases adenine, guanine, cytosine and thymine. Two opposite bases are called a base pair. 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 pair. For example, if the individual molecules on one strand form a DNA section "TAACGCCCTTA", this results in the sequence "ATTGGCGGGAAT" on the opposite strand.

The diagram above shows a section of a DNA strand. A phosphoric acid ester unit and a sugar unit form the backbone of a molecule (part of the blue band). Together with a base, these three units form a nucleotide (red ellipses). The two nucleotides (ellipses) form a macromolecule of the nucleic acid type deoxyribonucleic acid. In addition to their function as information storage, nucleic acids, which are regarded as the "key molecules of life", can also serve as signal transmitters or catalyse (support) biochemical reactions. The diagram below shows the human genome of a man (23 chromosome pairs = 46) with the sex-determining XY strand at the end (woman = XX).

Chromosom - Human Genom Male (Mann)

Chromosome 2 is the second largest chromosome in humans and consists of around 243 million base pairs. It contains about 8% of the total DNA of a human cell. 1,346 protein-coding genes and 1,239 pseudo-genes have been found. Pseudo-genes are genes that are no longer functional (switched off). Due to its size and the high number of known genes, many genetically determined or predisposed diseases are associated with the genes located on chromosome 2. For example, the MSH6 gene contains proteins in almost all living organisms that can recognise and cut out mismatches in DNA double strands.

Gene alphabet

The ladder is also known as the "gene alphabet", whereby the sequence of the base pairs plays an important role. The gene code is read (decoded) by the cell and used to build the proteins. The proteins consist of amino acids. The individual proteins have specific tasks. The sequence of base pairs determines how proteins are composed and how the organism is organised in detail. In humans, they determine appearance (e.g. body size, hair and eye colour) and characteristics (e.g. temperament, cause of illness and also the potential for a particular sport). However, environmental influences also play an equally important role when growing up. It is not yet clear whether genetics or environment play a more important role. The only thing that is clear is that there is an interaction and that, in terms of characteristics, one plays a greater role at one time and the other at another.

The DNA in the human genome is divided into 23 pairs of chromosomes, which occur in duplicate (homologous) (resulting in 46). One of the two chromosomes comes from the mother and one from the father. When the genome is passed on to the next generation, the mother passes on haploid chromatids created from her chromosomes in meiosis with newly combined genetic information to the child, which fuse with the genetically newly combined information of the father's haploid sperm cells resulting from meiosis to form the entire genome of the offspring when her egg cell is fertilised. In addition, individual sections can be exchanged during the inheritance process (crossing over), so that each person has an exclusive, unmistakable or "unique" genome pattern. A person's genome is not found a second time, except in the case of identical twins. 50% comes from the mother and 50% from the father.

Similarities between humans, animals and plants

Humans have around 25,500 genes, whereas water fleas have 30,000, so it is not the number of genes that matters, but how they are linked and interact. Incidentally, the DNA of all humans is 99.9% identical despite their individuality. The difference is only 0.1%, but this can still mean major differences in appearance and abilities. There is less genetic similarity between chimpanzees and orangutans than between chimpanzees and humans. However, the differences between humans and chimpanzees are ten times greater than between two humans.

DNA - Schimpanse, 6 Menschenköpfe, Weintrauben und Weíngläser

A European and a black African can be genetically more similar than two Europeans (for example, 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. The berry colour of grape varieties is also not a species characteristic; Pinot Noir, Pinot Gris and Pinot Blanc are strictly speaking a variety (see under Pinot). Incidentally, the DNA of a grapevine is 50% identical to that of humans. In principle, this applies to many plants. Many processes, such as metabolic processes, are identical in humans, animals and plants.

Grapevine genome

In August 2007, European researchers announced the decoding of the grapevine genome. This made it the first fruit-bearing plant whose DNA sequence is known. The scientists discovered a number of special features. The enzyme stilbene(aromatic hydrocarbon), which is responsible for the production of resveratrol, is present 43 times in the genome. The gene for the formation of terpenes exists in 89 variants. This is also the reason for the many different flavourings in wine. Wine contains more than twice as many genes for the production of oils and flavours as other plants. The individual flavour of the different grape varieties is therefore determined at the genome level.

A comparison with other genomes also shows which plants the grapevine is related to. According to this, the grapevine genome is made up of three predecessor genomes and is more closely related to poplar than to rice. Knowledge of the genome could also be helpful in the case of various vine diseases by using genetic engineering measures to create resistance to the microorganisms that cause them, such as bacteria and viruses.

Heterozygosity

The phenomenon of pronounced heterozygosity (also known as heterozygosity, heterozygosity, heterozygosity) is the reason for the individual appearance of each person and is equally typical of grape varieties. Spontaneous mutations result in small changes in the genetic information, which are passed on to the offspring and lead to the splitting of characteristics into many variants (alleles). Even cloned vines, which originate from vegetative propagation of a mother stock, can diverge due to mutations in the genetic material, which has frequently occurred in very old grape varieties such as Gouais Blanc (Heunisch), Muscat, Pinot and Traminer.

amereikanisch/europäische Hybriden

All varieties or genotypes of the vine subgenus Vitis have a double set of chromosomes with 2 x 19 = 38, i.e. all genotypes of the Asian vines (e.g. Vitis amurensis, Vitis coignetiae, Vitis ficifolia etc.), the European vines (Vitis amurensis, Vitis coignetiae, Vitis ficifolia etc.) and the European vines (Vitis coignetiae, Vitis ficifolia etc.).), European vines(Vitis vinifera) and most American vines (e.g. Vitis aestivalis, Vitis cinerea, Vitis labrusca, Vitis lincecumii, Vitis riparia, Vitis rupestris etc.). As they have the same number of chromosomes and there are no crossing barriers, they can be crossed with each other without any problems when breeding new grape varieties. However, there is also the American species Vitis rotundifolia with a different chromosome number of 2 x 20 = 40, which is why crosses between these species with reproductive offspring are very difficult, but have already been successful (see vine systematics).

Identification of grapevine varieties

For the identification of grape varieties and the clarification of parentage(mother variety and father variety), the genetic information at certain gene locations (gene locus, locus) within the DNA chain is used; see Grape variety identification and molecular genetics. The Nuclear Magnetic Resonance method was developed by the INRA Institute in 2002 to determine wine adulteration and the proportion of different grape varieties in a wine.

Cabernet Sauvignon - Kreuzung Cabernet Franc(Mutter) x Sauvignon Blanc (Vater)

Further information

For more information on this topic, see also American vines, Asian vines, flowering, chromosome, diploid, European vines, crossbreeding, molecular genetics, new breeding, vine family tree, vine systematics, taxonomy and breeding as well as a list of relevant keywords under grapevine. The graphic shows a double helix (chromosome section).

File:DNA orbit animated.gif

Scientific advice: Dr Volker Jörger
Sources 1: Onmeda, Simlpy Science,
Sources 2: WIKIPEDIA Deoxyribonucleic acid, chromosome and DNA
Genome: from Courtesy, NHGR, Public domain, Link
Grapes and glasses: from Photo Mix on Pixabay
Human heads: by Kollektiv, CC BY-SA 3.0, Link
Chimpanzee: by suju on Pixabay
Grape varieties: Ursula Brühl, Doris Schneider, Julius Kühn Institute (JKI)
Animated double helix: by Zephyris, CC BY-SA 3.0, Link

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