Step one: DNA isolation

All living creatures have genetic material in their cells that determines their characteristics and distinguishes them from each other. In animals, the carrier of genetic information is DNA (deoxyribonucleic acid). DNA molecule consists of a sequence of several billions of subunits called nucleotides, which, similar to the sequence of letters in books, gives instructions for the functioning of the organism. The amount of data in DNA within the subject is enormous and it cannot be routinely screened entirely. Therefore we use DNA tests to analyse DNA segments of interest.

An essential step in DNA testing is DNA isolation. It is the technique used to extract DNA molecule from a biological sample. The quantity, quality and integrity of DNA depend on the quality of the biological sample. It is crucial that the sample is as fresh as possible and contains a sufficient amount of biological material. Sample quality assessment is performed upon the admission to the laboratory and before DNA isolation. In our laboratory, DNA is mostly extracted from blood and buccal swab of an animal. A few drops of blood or a swab of the oral mucosa without visible mould and/or food debris are usually enough to successfully isolate DNA.

In animal cells, DNA molecule is organized in chromosomes within the cell nucleus. DNA isolation therefore involves physical and chemical approaches that allow DNA to be released from the cells and to be separated from other cellular components. DNA isolation process takes about two hours, can be manual or automated, and consists of three basic steps: lysis, precipitation, and purification. Lysis involves the mechanical disruption of cells and the enzymatic dissolution of cellular proteins. In the precipitation process, the alcohol is added to separate the released DNA from the cellular debris. In the last step, the released DNA is purified by washing away cell debris and reagents and stored at -20°C. Properly isolated and stored DNA can be used for genetic testing for many years.

A good quality DNA is crucial for successful performance of a genetic test. To be able to isolate good quality DNA in the laboratory, we need appropriate biological sample, therefore it is important to strictly follow the sample collection instructions available here. If DNA of sufficient quality cannot be isolated from the sample, a new sample is required to perform the genetic test.