DNA means deoxyribonucleic acid, which is an organic compound of a living being and some viruses. DNA is found in prokaryotic cells and the nucleus of eukaryotic cells, inside the chromosomes. The main function of DNA is to store genetic information for the construction of proteins and RNA that is essential for any vital function of an organism. The DNA stores and transmits from generation to generation all the information indispensable for the development of the biological functions of an organism.

Friedrich Miescherais was the first to isolate the DNA while experimenting with the chemical composition of pus from discarded surgical bandages.

However, it is not until 1952 that the experiments of Alfred Hershey and Martha Chase confirm the particular role of DNA in the inheritability.

DNA is a long polymer formed by repetitive units, the nucleotides. In living organisms it usually exists as a pair of closely associated molecules. The two strands of DNA are curled on themselves forming a kind of spiral staircase, called double helix. James Watson and Francis Crick proposed this double model in 1953 in the article «Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid.»

Depending on the complexity of each living organism, the DNA molecule will be larger and contain more information. It is emphasized that all members of a species share most of the information present in the DNA.

Thus, the DNA of all dogs from around the world is similar in more than 99% of its content.

The differences in that subtle 1% reach to explain not only the distinctions between the different races but also the differences between each animal individually. Therefore, the definitive characteristics of each DNA molecule are different for each living organism on Earth.