Self replication
Self-replication is a process in a system by which an object or structure makes a copy of itself. In contrast to auto -replication, self-replication denotes a completely autonomous reproduction without external help.
Natural self-replication in biology
The prototype of a self-replicating system is DNA . Cell division is a vital process for the growth of the entire body. Before each cell division, the DNA is doubled and part of it is passed on to the new cell. This ensures that the entire genetic information is stored in every cell. This self-replication process only takes a few minutes. Molecules self-replicate, so that genetic information is transmitted (inheritance). This happens because larger molecules act as templates for their formation from smaller molecules. Self-replicating molecules can thus catalyze their own formation.
In DNA replication, one strand of the double helix is first translated into a complementary strand. A copy of the original is only created when this strand is replicated. In contrast, most synthetic replicating systems are self-complementary; H. a copy of the original molecule is created directly during replication.
An important criterion for self-replication, which is based on an autocatalytic process, results from the so-called square root law. According to this, the speed at the beginning of the reaction (i.e. at low conversion) is proportional to the root of the concentration of the template added. This can be checked experimentally by measuring the reaction rate in the presence of different amounts of the pre-formed template.
Artificial Self-Replication in Organic Chemistry
At the beginning of life there were probably RNA - or RNA-like molecules, which must have fulfilled all vital functions including those of their own self-replication. In any case, this implies the hypothesis of an “RNA world”, which is said to have preceded today's “DNA-RNA-protein world” more than 3.5 billion years ago. The discovery of ribozymes , which was awarded the Nobel Prize in Chemistry, speaks for the RNA world . H. Ribonucleic acids (RNA) as enzymes, as well as the finding that short pieces of nucleic acids are capable of enzyme-free self-replication.
Both discoveries have led to important developments in chemistry: Today, catalytically active RNA molecules and RNA molecules with desired properties, like proteins, can be tailored in the test tube using evolutionary biotechnology. The elucidation of enzyme-free self-replication has ensured that chemists have meanwhile transferred the principle of self-replication to “foreign” structural classes, such as peptides and even abiogenic molecules. The use of biomolecules for programmable nanotechnology is also one of the fields of work that are now in the context of chemical research.
Artificial self-replication in technology and computer science
Self-replication is primarily the hallmark of living systems, although no longer exclusively. Although most attempts at self-replicative automata or algorithms fall under the term auto-replication, over time there has been an increasing degree of autonomy, which blurs the boundaries.
Scientific studies of self-replicating structures or machines were first published in 1929 by JD Bernal and by mathematicians such as Stephen C. Kleene , who began developing recursion theory in the 1930s. Although originally driven by an ongoing interest in biology, much of his work was inspired by a desire to understand the fundamental information processing principles and algorithms involved in self-replication, even regardless of their physical realization.
When discussing the self-replication of automata, it is essential to lay down important basic rules from the outset. For example, according to Kemeny: “If by the term 'reproduction' we mean the creation of an object like its original from nothing, then no machine can reproduce itself - but neither can a human. The characteristic feature of the reproduction of life is that the living organism can create a new organism, as it is itself, from immobile matter surrounding it. "
From the point of view of computer science, John von Neumann was one of the first to give scientifically sound considerations to a hypothetical, replication-capable robot in the 1940s. However, this purely theoretical concept could not be implemented in practice. In 1953 he therefore developed the theory of self-reproducing automata (published after his death by Burks in 1966 as Theory of Self-reproducing Automata ) as a model for a software-based solution of self-replication that can be implemented using computer technology.
Artificial self-replicating software first appeared in the 1960s, and multiplied very quickly in later decades in the form of viruses, worms, and most importantly, programs dealing with artificial life .