Editing Self-replication (section)

===Theory===
{{See also|Von Neumann universal constructor}}

Early research by [[John von Neumann]]<ref name=Hixon_vonNeumann>{{cite book|last=von Neumann|first=John|title=The Hixon Symposium|year=1948|location=Pasadena, California|pages=1–36}}</ref> established that replicators have several parts:

*A coded representation of the replicator
*A mechanism to copy the coded representation
*A mechanism for effecting construction within the host environment of the replicator

Exceptions to this pattern may be possible, although almost all known examples adhere to it. Scientists have come close to  constructing [https://arstechnica.com/science/2011/04/investigations-into-the-ancient-rna-world/ RNA that can be copied] in an "environment" that is a solution of RNA monomers and transcriptase, but such systems are more accurately characterized as "assisted replication" than "self-replication". In 2021 researchers succeeded in constructing a system with sixteen specially designed DNA sequences. Four of these can be linked together (through base pairing) in a certain order following a template of four already-linked sequences, by changing the temperature up and down. The number of template copies is thus increased in each cycle. No external agent such as an enzyme is needed, but the system must be supplied with a reservoir of the sixteen DNA sequences.<ref name="EL-20210302">{{cite journal |last1=Kühnlein |first1=Alexandra |last2=Lanzmich |first2=Simon A. |last3=Brun |first3=Dieter |title=tRNA sequences can assemble into a replicator |doi=10.7554/eLife.63431 |pmc=7924937 |date=2 March 2021 |journal=[[eLife]] |volume=10 |pages=e63431 |pmid=33648631 |doi-access=free }} For an interpretation in terms of the origin of life, see {{cite news |last=Maximilian |first=Ludwig |title=Solving the Chicken-and-the-Egg Problem – "A Step Closer to the Reconstruction of the Origin of Life" |url=https://scitechdaily.com/solving-the-chicken-and-the-egg-problem-a-step-closer-to-the-reconstruction-of-the-origin-of-life/ |date=3 April 2021 |work=[[SciTech (magazine)|SciTechDaily]] |accessdate=3 April 2021 }}</ref>

The simplest possible case is that only a genome exists.  Without some specification of the self-reproducing steps, a genome-only system is probably better characterized as something like a [[crystal]].