DNA Microchip Technology

DNA Microchip Technology

DNA computers can't be found at your local electronics store yet. The technology is still in development, and didn't even exist as a concept a decade ago. In 1994, Leonard Adleman introduced the idea of using DNA to solve complex mathematical problems. Adleman, a computer scientist at the University of Southern California, came to the conclusion that DNA had computational potential after reading the book "Molecular Biology of the Gene," written by James Watson, who co-discovered the structure of DNA in 1953. In fact, DNA is very similar to a computer hard drive in how it stores permanent information about your genes.

Adleman is often called the inventor of DNA computers. His article in a 1994 issue of the journal Science outlined how to use DNA to solve a well-known mathematical problem, called the directed Hamilton Path problem, also known as the "traveling salesman" problem. The goal of the problem is to find the shortest route between a number of cities, going through each city only once. As you add more cities to the problem, the problem becomes more difficult. Adleman chose to find the shortest route between seven cities.

What is a DNA microchip?
"DNA chip" is slang for DNA microarray.


DNA chips are a revolutionary technology. They speed up research, helping scientists understand the primary sequence of the human genome, now almost complete. They will also allow doctors to get important genetic information from individual patients and thus choose the best treatments.
Each of the strands in a bit of double-stranded DNA is complementary to the other. Adenine (A) is opposite thymine (T), cytosine (C) is opposite guanine (G). So, the sequence CCATGA would be complementary to GGTACT. Complementary DNA strands separate on gentle heating. They bind again when cooled.
A DNA chip is made of many different DNA sequences stuck to a flat surface. Each spot on the surface contains a different sequence.
You can use a single strand of DNA to "probe" a solution for that strand's complement: Put in the probe, slosh it around, pull it out. If the complement is in there, it will bind onto the probe.



What is a DNA microchip used for?

Because chip technology is still relatively new, it is currently only a research tool. Scientists use it to conduct large-scale population studies - for example, to determine how often individuals with a particular mutation actually develop breast cancer.


Researchers love DNA chips because they give a huge amount of information, fast, at low cost.
Doctors will soon learn to love them because there are many times when a doctor would like to know something about a patient's genes (such as whether the patient is likely to respond well to a certain drug). When the price comes down enough, microarrays will likely become routine tools in the doctor's office.



How does a DNA microchip work?

A DNA microarray allows you to probe a solution for thousands of different sequences all at once. Stick each different probe at a specific spot on a flat surface. Slosh a solution containing the unknown single-stranded sequence over it. Rinse. Look for the spots where the probes found their complements.
Microarrays can have tens of thousands of spots. This means they can look for tens of thousands of DNA sequences all at once.
A sequencing array is made of many different short DNA sequences. Researchers use these to find the sequence of an unknown bit of DNA. A researcher chops the unknown sequence into short bits, sees where the bits bind on the array, deduces the sequences of all the short unknown bits, then reassembles the overlapping sequences into one long sequence.
An expression array is made up of many different long DNA sequences, each complementary to every mRNA sequence that a certain cell can make. Researchers use these to study moment-to-moment changes in which genes are turned on or off. A researcher breaks a cell preparation open, extracts all the mRNA sequences it contains at that moment, and puts those on the expression array to see which ones are there. This tells the researcher which genes in the cell were turned on-being expressed, making mRNA-at the moment the cell broke open.


How are DNA microchips better than silicon microchips?

• DNA computers show promise because they do not have the limitations of silicon-based chips.
• DNA based chip manufacturers will always have an ample supply of raw materials as DNA exists in all living things; this means generally lower overhead costs. 
• DNA chip manufacture does not produce toxic by-products
• DNA computers will be much smaller than silicon-based computers as one pound of DNA chips can hold all the information stored in all the computers in the world.
• With the use of DNA logic gates, a DNA computer the size of a teardrop will be more powerful than today's most powerful supercomputer.
• A DNA chip less than the size of a dime will have the capacity to perform 10 trillion parallel calculations at one time as well as hold ten terabytes of data.
• The capacity to perform parallel calculations, much more trillions of parallel calculations, is something silicon-based computers are not able to do. As such, a complex mathematical problem that could take silicon-based computers thousands of years to solve can be done by DNA computers in hours. 

                                                                                                                                            Source :HSW