DNA laddering is a phenomenon seen in laboratory tests; it is a sensitive indicator of programmed cell death

Programmed cell death

Programmed cell-death is death of a cell in any form, mediated by an intracellular program. PCD is carried out in a regulated process which generally confers advantage during an organism's life-cycle...

, specifically of apoptosis

Apoptosis

Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...

. It was first described in 1980 by A. H. Wyllie at the University of Edinburgh Medical School

University of Edinburgh Medical School

The University of Edinburgh Medical School is part of the College of Medicine and Veterinary Medicine of the University of Edinburgh. Established nearly 283 years ago, Edinburgh Medical School is one of the oldest medical schools in Scotland and the UK...

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Endonuclease

Endonuclease

Endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain, in contrast to exonucleases, which cleave phosphodiester bonds at the end of a polynucleotide chain. Typically, a restriction site will be a palindromic sequence four to six nucleotides long. Most...

 activation is a characteristic feature of apoptosis. This degrades genomic DNA at internucleosomal linker regions and produces 180- to 185- base-pair DNA fragments. On Agarose gel electrophoresis, these give a characteristic "laddered" appearance. The dying cell's morphological changes

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

 are short-lived and difficult to detect. DNA laddering has therefore become a sensitive method to distinguish apoptosis

Apoptosis

Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...

 from ischemic

Ischemia

In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...

 or toxic cell death

Necrosis

Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...

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