DNA laddering

DNA laddering is a distinctive feature of DNA degraded by caspase-activated DNase (CAD), which is a key event during apoptosis. CAD cleaves genomic DNA at internucleosomal linker regions, resulting in DNA fragments that are multiples of 180–185 base-pairs in length. Separation of the fragments by agarose gel electrophoresis and subsequent visualization, for example by ethidium bromide staining, results in a characteristic "ladder" pattern. A simple method of selective extraction of fragmented DNA from apoptotic cells without the presence of high molecular weight DNA sections, generating the laddering pattern, utilizes pretreatment of cells in ethanol. ==Apoptosis and necrosis==

While most of the morphological features of apoptotic cells are short-lived, DNA laddering can be used as final state read-out method and has therefore become a reliable method to distinguish apoptosis from necrosis. DNA laddering can also be used to see if cells underwent apoptosis in the presence of a virus. This is useful because it can help determine the effects a virus has on a cell. DNA laddering can only be used to detect apoptosis during the later stages of apoptosis. This is due to DNA fragmentation taking place in a later stage of the apoptosis process. It is also important to note that DNA laddering occurs differently depending on the type of cell, so there may be slight changes in the process of DNA laddering depending on the cell that is being investigated. == See also ==