How mutations happen in the evolution of species?

The individual characteristics are inherited through the genes, chemical entities present in the cells, including those intended for the reproduction of the body. To the total number of genes, also called genetic heritage, correspond all the individual inheritable physical characteristics.
The genes are linked to one another in a long chain forming  the DNA molecule. This molecule has the ability to replicate, thus duplicating the genes as well. It is possible, although it is a rare phenomenon, that a mistake occurs in that duplication and this leads to the modification of a gene. Mutations can be also caused by physical or chemical agents as external radiation, viruses and other things that are called mutagen. The alteration of a gene is called mutation and may result in the emergence of a new individual feature.
The structure of an organism is a very complicated architecture in which an arbitrary change of a gene can have the most disparate effects; it will be disastrous if compromises the functioning of a gene that plays a strategic and fundamental role (like genetic diseases), while the effects will be less deleterious if the mutated gene has a more marginal role, up to the case when no harmful effect is there, as it may be the case of the emergence of a new nuance of eye color. The genetic characteristics of an organism are enormously numerous as well as the possible mutations, including those harmless. These mutations, just because harmless, will not be eliminated by natural selection and therefore roll over time giving rise to great variability of individual characters (almond eyes, protruding cheekbones, receding chin, taurine neck etc.). The greater the variety is, the greater will be the chance that some feature is useful in the event of an environmental change (for example, the color of the skin, hair and eye for men who have colonized the northern regions of the planet).
It should be noted that mutations play a key role in the evolution of species as natural selection provide the material to work on. Without mutations, natural selection tends only to standardize the most of existing genetic heritage without further changes. On the other hand, we can say that without selection even natural mutations alone could not lead to the phenomenon of  evolution of species, but only to an increase in individual genetic variability with new purely random combinations.

FURTHER INFO
   DNA,   GENE,  MUTATION,  RADIATION,  VIRUS

ROYAL BOX
   GREGOR MENDEL  

ABSTRACTS
   n. 1 – NATURAL SELECTION AND MUTATIONS

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