DNA Computers
 

Introduction  
In 1994, USC professor, Leonard Adleman set out to solve the “Traveling Salesman” math problem utilizing DNA as the source for the computations.  The crux of this problem was to find the optimal path by which a traveling salesman could visit a fixed number of cities, but none of the cities could be visited more than one time. His computational success in solving this problem has propelled the research in the field of DNA Computers. 

DNA computers utilize the four chemical base pairs, represented by the letters A (adenine), C (cytosine), T (thymine), and G (guanine) that form the double-helix molecule that stores and processes the encoded blueprints for all living organisms.  Because each DNA molecule is an ultra-dense system, packing megabytes of information equivalent to a little computer chip and roughly the size of a silicon transistor, the field of DNA computing holds great promise as a possible, future replacement for the computer and the silicon chip.  Therefore, this natural form of data storage has become the thrust of Adleman’s research and many other scientists as well. 

Differences Between Conventional and DNA Computers
There are several notable differences between the DNA computer and the conventional computers used today.  Conventional computers represent information in terms of 1's and 0's, physically expressed in terms of the flow of electrons through logical circuits, whereas DNA computers represent information in terms of the chemical properties of DNA. Computing with a conventional computer is done with a program that instructs electrons to travel on designated paths; with a DNA computer, the input and output are both strands of DNA, whose genetic sequences encode certain information. The execution of the DNA computer's "program" is a series of biochemical reactions, which have the effect of synthesizing, extracting, modifying and cloning the DNA strands and letting them react in test tubes or on a glass slide coated in 24K gold.

The potential power of these DNA molecules may be the key to solving complex mathematical problems with greater efficiency than the most advanced silicon chips. When a regular computer attacks a problem, it evaluates each possible answer separately or in a linear fashion, solving the formula over and over again until it finds the right answer. A difficult problem can take months and this is a huge advantage for using a DNA computer, because every possible answer is evaluated simultaneously. It's a method known as parallel processing, used by only the world's most powerful supercomputers. (Source:  http://www.cs.iupui.edu/~pellison/n301/how.html)

How DNA Computers Work
The DNA computer works by enzymatically forcing DNA molecules to generate different chemical states.  These molecules are then mixed in a test tube and within a few seconds, all possible DNA combination strands will begin sticking together. Each chain of DNA represents a possible answer, which is further examined by eliminating the wrong molecules through further chemical reactions, leaving behind only the correct answer.

Future Uses of DNA Computers
Early DNA computers will probably not be used as a word processor or for email purposes, but because of its ability to solve complex mathematical problems in a relatively short time frame, DNA computers will be used to crack coded messages encrypted with the U.S. government's Data Encryption Standard.  This encryption standard is used to protect a wide range of data, including telephone conversations on classified topics and data transmissions between banks and the Federal Reserve. Testing all possible combinations using an electronic computer can be accomplished today, but would take an enormous amount of time.  However, a highly automated DNA computer may some day be able to crack the code in under two hours.  In addition, DNA computers may be very useful in medicine in hope that a DNA computer could deliver drugs inside the human body, control medical devices, or store enormous databases like the human genome.  The future of DNA computing looks promising, however it may be years before we see its potential become a reality. Source: http://www.cs.iupui.edu/~pellison/n301/page3.html)

Helpful Links

Biomolecular Computers This website contains a thorough, easy to read description of DNA Computers

DNA Computing: A Primer  Excellent demonstration of the "Salesman" problem

Smaller Computing Through DNA  A good article on DNA computing that contains a 3 minute video clip on the making of DNA computers

Blowing Past Conventional Computing  A comparison between DNA computing power and conventional computers

How DNA Computers Will Work  An article from HowStuffWorks

Time to Engineer DNA Computers  An interview with Leonard Adleman, the man who invented the DNA Computer

Test Tube Holds a Trillion Computers  1 of 2 articles from BBC News discussing DNA Computers

DNA Computers Take Shape  2of 2 articles from BBC News discussing DNA Computers

DNA-Based Computer Solves Truly Huge Logic Problem  An article about a DNA-based computer that solved a logic problem that no person could complete by hand