Introduction

According to Darwin’s theory of natural selection, creatures, forms of life and organisms that are better adapted to their environment tend to survive longer. The stronger they are the more chance the will have for racial preservation and self-support. Natural selection – adaptability and changing qualities as well as attributions – affects both wild animals and human beings.

Physical activities played a crucial role in getting food, thus surviving. Our ancestors’ hunting lasted for several days and while hunting they covered long distances. Moreover they were not inactive either while resting. Hominids’ energy needs was 49-50 kcal/kg. By contrast nowadays human beings need 32-33 kcal/kg daily. Our physical activity developed through evolution lasting millions of years. The result of natural selection led to direct changes in genetic stock which enhanced adaptability to natural conditions.

Genetics, -nowadays the expression of genomics is used- the science of biology deals with the heredity transmission of organisms and their regularity variations. The structure of genome, the organization of chromatin, functions of genes, the frequency of recombination, and mutational changes are also examined. By the beginning of 2000 the Human Genome Project (HGP) was finished. With the help of this the mapping of human genome could be carried out. Now the sequence of billion nucleotides of human DNS 3 is known. It turned out that it contains a little more than 20 thousand genes. These genes, almost the 2% of the whole genome stock, encode the proteins of our body. Genetic code is a set of rules defining the sequence of the four letter codes/language of DNS- molecule: adenine (A) thymine (T), cytosine (C), guanine (G). They encode the sequence of the 20 different amino acids, the primary structure of proteins. This code, the nucleotide sequence, provides the qualities of humans, and the foundational differences of individuals. The uniqueness of individuals is formed by three factors at genomic level:

1. The difference in the sequence is about 0.1% which means that within 10000 nucleotides only one is different. This difference is called Single Nucleotide Polymorphism (SNP). Most commonly we speak about ANP if variation of the population frequency is over 1%. The lower variation is mutation.
2. A little bigger (1-3%) rate of individual difference is possible in longer DNS sequence repeat regarding their number and place. It is called CNV (copy number variant). The structural variants of genome belong to CNV.
3. The third difference does not occur in the sequences but in the secondary chemical change of DNS, e.g.: methylation, or in certain alterations of proteins attached to DNS, e.g.: acetylation. It is called epigenetic modification.