Eucaryote chromosomes are linear structures built out of the DNA molecule which holds the entire genetic information of an organism and its proteins. Although highly susceptible to damage and breaks, eucaryote cells have very efficient systems of repair. In case of a faulty DNA repair the cell will most probable die, but in some cases the cells begin to grow and divide uncontrollably in such a way that they push and smother other healthy tissue. The topic of this paper is tumors caused by chromosomal aberrations. Chromosomal aberrations most responsible for the creation of tumors can be divided in to translocations an aneploudis. Translocations are nonhomologues exchanges of various pieces of chromosomes, this most frequently happens during a faulty DNA repair process. The causes of breaks may be external or internal but the result is the same the creation of a faulty chimerical protein or a over abundant expression of a certain protein which leads to a state of imbalance. Aneplodi is defined by a multiplication or lack of a single chromosome which produces an abnormal number of chromosomes per set common for a certain species and causes large instability, partially due to the large part of the genome involved, and because of the production of a misbalanced amount of proteins. The most common cause of aneploidy is an error during mitosis and disproportional segregation of chromosomes between mother and daughter cells. Cancer is one of the least well understood diseases of the twenty first century which annually claims over one fourth of all deaths in the western world . More than a fifth of all tumors are caused by chromosomal aberrations, and almost all tumors have chromosomal aberrations in the later stages.