# Reprogrammable DNA Computers Are Now a Reality

Before we can talk about DNA computers we first have to know a bit about the basics of how a computer, any computer, works. Because a DNA computer is often referred to as a biological computer, it needs to be understood as a living computational device. Since all living things grow and change, any true biological computer will grow and change over time. This is where part of its vast potential lies. Every computer must be able to perform 7 basic computational tasks to have any meaningful value. Those 7 tasks are:

• AND is True if: A and B are both True
• OR is True if: either A or B are True
• NOT inverts the value as follows: True if the input is False; False if the input is True
• XOR is True if: either A or B are True, but False if both are True
• NAND is an AND value followed by a NOT and is False only if A and B are both True
• NOR is a OR followed by a NOT and is True only if: A and B are both False
• XNOR is an XOR followed by a NOT and is True if: either A and B are both True or both False

True and false are what most people associate with the basics of computer science (1 = ON = true; 0 = OFF = FALSE). These 7 tasks are known as Logic Gates and are the result of the input of 2 digital values (1+1, 0+0, 1+0, 0+1). What makes a computer so powerful is that it is able to make these computations and comparisons at a very fast rate. Back in 1997 the first DNA Logic Gates were created in a biological computer, considered a major breakthrough then.

The most recent discovery came when it was found that the “growing” part of the biological computer can be used as a mechanism for growing as the computer is doing real time computing. The name of the concept (not the machine) is a Nondeterministic Universal Turing Machine or (NUTM).

Two key concepts are important to understand on how the NUTM actually works. The first is simple. DNA molecules are extremely small and therefore take up very little physical space. This gives a NUTM the advantage of using more processors since the required physical space, say on a desktop, will be very small. The second concept is that the energy required to perform all these vast numbers of computations is also very small, making any NUTM system extremely energy efficient.

Finally, the DNA growth is controlled by managing the number of paths created that will direct the DNA replication to achieve a specific result. Thus, as the DNA grows, the growth will be directed to employ the Logic Gates, much like electricity is channeled through a wire and produces the results we currently take for granted every day.

There is a limitation that has slowed development of DNA computing which is not so difficult to see. If a DNA growth is used to direct growth to a specific solution, the DNA computer will be limited to solving a single problem at a time. What scientists at the University of California, Davis, have done is to create 355 different “tiles” where each tile is similar to an electronic circuit in a modern computer. The tiles will theoretically be able to direct the growth based on the problem needed to be solved.

A typical computer application is able to perform multiple functions at the same time due to the number of available circuits in the processor. For example, when your computer selects items from a list, it runs through the Logic Gates to make its selection. Though in its infancy, the researchers have been able to develop a total of 21 simple applications with the existing tiles.

Those of us who are keeping up with artificial intelligence have seen the potential for both good and bad coming forth from it. But all this time we have been dealing with non-living materials. A DNA/biological computer will be an actual living program. Though its potential to replace existing technology is still decades away, it is time for us to consider what type of controls are necessary to prevent yet another creation of man from controlling our lives rather than the reverse.