Decomposition and DNA
Location: Outside U.S.
Date: Summer 2012
How does the decomposition of an organism affect the amount of DNA that can be retrieved from it?
In general, decomposition of an organism occurs through non-living as
well as living processes. I am sure you are familiar with
microorganisms like bacteria which digest the body's cellular
components as food. In addition to this, chemical reactions can
spontaneously occur that break down the organism's molecules through
processes such as hydrolysis.
Normally, this would mean that as the body is decomposed, nearly all
of the genetic material would likely be digested by bacteria or broken
down by natural processes. Some tissues - notably bone and cartilage
- are resistant to decomposition, because they contain largely
undigestible material. As such, DNA has been extracted from the bones
of decomposed bodies decades after death to use for forensic purposes
(i.e. to identify remains). It can be difficult to isolate sufficient
quantities of undamaged DNA, though, and it becomes more challenging
for remains from further in the past.
In addition, the preservation of DNA is highly dependent on the
environmental conditions during and after decomposition. Extremely
cold and dry conditions can help preserve cellular components for
later analysis, as has been the case with some prehistoric animals and
people who were relatively well preserved after a very long period.
S. Unterman Ph.D.
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Update: November 2011