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- DNA (Desoxyriboneucleicacid)
- The principle of the evolution
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| fig. 1.1.1: A DNA molecule |
DNA is a long drawn, spiral shaped molecule. A DNA molecule consists of two chains of alternate a phosphate group and a sugar (desoxyribose). To each sugar a nitrogen base is linked. The nitrogen bases of the two chains are linked two and two. There are four nitrogen bases: adenine (A), thiamine (T), cytosine (C) and guanine (G). In a DNA molecule always the bases A and T are connected, just as the bases C and G. These bases form fixed pairs. A nitrogen base, a phosphate group and a saccharic acid together form a nucleotide. A DNA molecule consists of two chains of millions of nucleotides. These chains are wound in a spiral.
In the order in which the nitrogen bases in a DNA molecule are ranged, sometimes a sudden change can appear. Because of this a gene can change. A gene or a hereditary factor is a part of a DNA molecule that contains information about one particularly hereditary quality. Such a change is called a mutation. An individual person, by whom a mutation appears in his appearance, is called a mutant.
Basically DNA is the code every cell in an organism contains and that determines the characteristics of an organism. At the propagation the characteristics of the parents are being past on to the offspring. At the point that a spermatozoon of, for example a human being, containing the code of the father, fuses with an ovule, containing the code of the mother. These codes are being merged to a new code of the child. In case within these codes so-called 'letters ' change and new types of letters are being generated, new characteristics come into being. Those changes in the letters are being called mutations. So mutations cause hereditary changes in species. Mutations can be favourable or unfavourable. Favourable mutations in general make an organism stronger. A favourably mutated organism is better adapted to its environment. In those circumstances the mutants can propagate easier then the original species. Ultimately the original species will extinct and the evolved species remain. This is the principle of 'survival of the fittest' and of 'natural selection'. Most mutations however are unfavourable and can have a devastating effect on the species.
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