DNA Computing

DNA Computing

Introduction:

“Come forth into the light of things. Let nature be your teacher.” - Wordsworth
A brief look at the history of humanity shows that since the earliest days, people needed to count and compute, either for measuring the months and the seasons or for commerce and constructions. The means used for performing calculations were whatever was available and thus gradually progressed from manual to mechanical and from there on to electrical devices.
Indeed, man started off by counting on his digits. The abacus was man’s first attempt at automating the counting process, and it involved the idea of positional representation. The transition to a qualitatively superior way of doing computation had to wait until the 17th century when Pascal built the first mechanical adding machine based on a gear system.
Later on, Charles Babbage theorized but never built a fully automatic steam driven calculating machine and an analytical engine that would have conditional control and where the instructions were to be stored on punched cards. The introduction of the punched cards by Herman Hollerith marked the transition from the decimal system to the binary system. The binary system had two states, and corresponding to the place in the card having or not a hole punched in to it. The binary representation could take advantage of many two-state devices like card readers, electric circuits (on/off states) and vacuum tubes, and it led to the next stage in the evolution of computing: the electronic one.
The first high-speed electronic digital computer was the ENIAC, which used almost 18000 vacuum tubes, had input/output on punch cards and could perform a few arithmetical operations. However, the instructions of a program had to be wired in separately for each problem. John von Neumann addressed this issue and laid the principles of how a practical computer should be organized and built. His main ideas were the introduction of a conditional go-to instruction and the storing of the data and the program together in the same memory unit, which meant that the machine itself could alter either its data or program.
This led to the first generation of modern programmable electronic computers which used random access memory RAM. It was two technological advances, the discovery of the transistor and building of the first integrated circuits that truly released the potential of electronic computers. But, even electronic computers have their limitations, there is only so much data they can store and their speed thresholds determined by physical laws will soon be reached. The latest attempt to break down these barriers is to replace (once more) the tools for doing computations, instead of electrical use biological ones.
Research in this area was started by Leonard Adleman in 1994, when he surprised the scientific community by using the tools of molecular biology to solve a hard computational problem (Adleman’s experiment) solving an instance of the Directed Hamiltonian Path Problem solely by manipulating DNA strands, marked the first instance of a mathematical problem being solved by biological means. The excitement DNA computing incited was mainly caused by its capability of massively parallel searches. This, in turn, showed its potential to yield tremendous advantages from the point of view of speed, energy consumption and density of stored information.
A few more words, as to why we should prefer biomolecules to electricity for doing computation: the short answer is that it seems more natural to do so. We could look at the electronic technology as just a technology that was in the right place at the right time indeed, electricity hardly seems a suitable and intuitive means for storing information and for computations. For these purposes, nature prefers instead a medium consisting of biomolecules. DNA has been used for millions of years as storage for genetic information, while the functioning of living organisms requires computations. Such considerations seem to indicate that using biomolecules for computations is a promising new avenue, and that DNA computers might well be the successors of electronic computers.


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