Chromosomal aberrations and cancer

Abstract

Kromosomi eukariota su linearne strukture građene od molekule DNK koje sadrže ukupnu genetičku informaciju organizma i proteina. Iako su podložni oštećenjima i lomovima, eukariotska stanica ima vrlo efikasne sustave popravka. U slučaju neispravnog popravka DNK, stanica može umrijeti no u nekim slučajevima stanice se počnu nekontrolirano dijeliti i rasti, te istiskivati i izgladnjivati okolne stanice zdravog tkiva. Ovaj seminar govori o tumorima uzrokovanim kromosomskim aberacijama. Kromosomske aberacije najvažnije za nastanak tumora možemo podijeliti na translokacije i aneuploidije. Translokacije su izmjene nehomolognih dijelova kromosoma, najčešće prilikom neispravnog popravka dvostrukih lomova DNK. Uzroci lomova mogu biti vanjski i unutrašnji, no rezultat je isti: ili stvaranje neispravnog himernog proteina ili prekomjerna ekspresija proteina koja dovodi do stanja neuravnoteženosti. Aneploidija se javlja kad stanica ima više ili manje kopija određenog kromosoma te odstupa od normalnog broja kromosoma za određenu vrstu, te se zbog povećane količine genetičke informacije javlja ekstremna neuravnoteženost u količini produkata zahvaćenih gena. Najčešći uzrok aneuploidije je greška prilikom mitoze stanica i neispravna segregacija kromosoma. Rak je jedna od najmanje shvaćenih bolest dvadeset i prvog stoljeća kojoj se svake godine pripisuje četvrtina svih smrtnih slučajeva u zapadnome svijetu. Više od petine svih tumora uzrokovano je kromosomskim aberacijama, a skoro svi tumori u kasnijim fazama pokazuju velike aberacije kariotipa.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