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Name: Maddison
Status: student
Grade: 12+
Location: Outside U.S.
Country: Australia
Date: Summer 2012


Question:
How does the decomposition of an organism affect the amount of DNA that can be retrieved from it?



Replies:
Maddison,

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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