Ask A Scientist© Molecular Biology Archive

name         Courtney
status       student
age          20s

Question -   Does EVERY living thing replicate
itself through DNA? 
Are there non-living things that replicate themselves?

There are viruses that replicate with RNA but they
need to go through a stage of DNA when inside a host
cell.

Non-living things that replicate themselves? I had a
discussion with a geologist once who gave the example
of crystals, that produce self-like crystals from
non-crystalline material. The basic components of
rocks are used and reused in eternal cycles, crystals
are formed, stable for a limited time, then degraded
and their material is reused for new crystals. They
are clearly not alive, but what defines that they are
not? They don't move, but so don't do trees. They
don't always produce identical offspring, but not one
mold looks alike its sister. In fact, the only
argument I could come up with is that they are not
composed of organic material (C, H, O and some odd
elements) and that there is no energy metabolism. The
geologist would argue the latter: there certainly is
crystallization energy involved. Could you come up
with a better argument that defines living forms?

Trudy Wassenaar
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Yes, all living things require DNA to replicate themselves.  As for
non-living things, there is some semantic debate as to whether viruses are
living or not.  Not all viruses contain DNA, but those that do not contain
RNA, which must be transcribed into DNA to replicate the virus.

Recently, chemists have produced some synthetic chemical systems that
"self-replicate" in a limited sense (see Andrew Robertson, Andrew J.
Sinclair, and Douglas Philp. "Minimal Self-Replicating Systems." Chemical
Society Reviews 29 (1999): 141-52 for more detail).

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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