Difficulties derived from the big complexity of the human genome (because of the great amount of genes) and difficulties at the time of performing a correct molecular diagnosis have led to the utilization of advanced technologies such as DNA arrays. By this technique, it is possible to analyze in a single experiment great sequences of genomic regions, to detect mutations or polymorphisms (characteristic of each individual), and to analyze variations in the expression of genes implicated in different disorders or in the utilization of drugs. Similarly, the use of DNA arrays-derived information has led to a considerable advance in the personalized medicine that is applied to every patient, avoiding unwanted adverse effects and the consecution of the best performance effectiveness for each drug.