Complexity of genetic material
The body of an organism consists of a large number of cells, which contain a full and complete set of genetic material. Genetic information is present in the nucleus of a cell. The genetic information is stored in chromosomes, which are translated by the body in useful data (proteins). This happens constantly in all cells. The general code is called DNA.
Chromosomes exist of long DNA-strains which are wound around each other very tightly. When a chromosome is studied in detail, it is possible to look at the composition of DNA in the form of A, T, G, or C. These A, T, G and C are the building blocks from which the DNA is constructed. Sometimes stretches of repeats are present (e.g. CACACA) – such stretches are indicated as microsatellites (also known as STRs). Other variation such as G/A or C/G is indicated as Single Nucleotide Polymorphism (SNP). The order and composition of DNA are the basis for all kinds of applications.
For the typing of the composition of genetic characteristics it is possible to use hairs, feathers – to be drawn with roots –, blood, milk, tissue etcetera. The usability of sample material depends on the test which is carried out. The use of ‘fresh’ material provides the best result.
Techniques
Genetic variation can be visualized with a number of different techniques. Frequently a technique is used, where DNA is multiplied (PCR). DNA can be made visible through three steps:
- DNA-extraction, where the cells are broken into small pieces. The DNA is present in an aqueous solution, which is necessary to enable a successful PCR-reaction,
- Selective multiplying of DNA, where PCR is used to multiply small specific pieces,
- Analysis of DNA on a machine, with which DNA is visualized. For that purpose, fluorescence is incorporated during PCR.
The final result of these steps results generally in the detection of the variation in STRs or SNPs. By examining a number of STRs or SNPs, a genetic bar code is generated. This bar code can be used for a number of different tests, among which are lineage, identity of samples, etcetera. In a number of examples these applications are described below.
