The amount of DNA per nucleosome was determined by treating chromatin with an enzyme that cuts DNA (such enzymes are called DNases). One such enzyme, micrococcal nuclease (MNase), has the important property of preferentially cutting the linker DNA between nucleosomes well before it cuts the DNA that is wrapped around octamers. By regulating the amount of cutting that occurs after application of MNase, it is possible to stop the reaction before every linker DNA has been cleaved. At this point, the treated chromatin will consist of mononucleosomes, dinucleosomes (connected by linker DNA), trinucleosomes, and so forth. If DNA from MNase-treated chromatin is then separated on a gel, a number of bands will appear, each having a length that is a multiple of mononucleosomal DNA. The simplest explanation for this observation is that chromatin possesses a fundamental repeating structure. When this was considered together with data from electron microscopy and chemical cross-linking of histones, the "subunit theory" of chromatin was adopted.