There are three ways that aneuploidy can occur. It can occur due to loss of a whole chromosome, gain of a whole chromosome or rearrangement of partial chromosomes known as gross chromosomal rearrangements (GCR). All of these are hallmarks of some cancers.[5] Segmental aneuploidy can occur due to deletions, amplifications or translocations, which arise from breaks in DNA,[2] while loss and gain of whole chromosomes is often due to errors during mitosis.