Just imagine a time when one will know, from the second a person is born, whether they will ever have a heart attack or develop Diabetes in their lifetime. Just imagine a time when a doctor, sitting in his clinic, would know the one exact drug needed to eliminate an infection without creating resistant organisms or whether or not a patient with cancer would respond to a particular treatment without even initiating it first, sparing the patient of unnecessary harm. Just imagine a time when culprits could be identified from blood samples within seconds of the crime. With the development of DNA-chips, these far-fetching possibilities may become realities of the near future.
What are DNA chips?
Also known as micro-assays & bio-films, DNA-chips are small, solid supports onto which the sequences from thousands of different genes are immobilized. The supports could be made of glass microscope slides, silicon chips or nylon membranes. Using this technique specific gene sequences could be identified and their particular expression levels could be determined.
How do they work?
The core principle behind microarrays is hybridization between two DNA strands. First of all the DNA in the sample is denatured- a process that separates the two complementary strands of DNA into single-stranded molecules. These strands are then cut into smaller, more manageable fragments and then labelled by attaching it to a fluorescent dye. It is then mixed with the gene sequences on the chip and allowed to hybridize. After washing off of non-specific bonding sequences, only strongly paired strands will remain hybridized. These fluorescently labelled target sequences that bind to a probe sequence generate an optical signal which can be picked up and analysed to determine the exact gene sequences in the un-identified sample.
What’s so special about these “chips”!
Previously, techniques including “Southern blotting” were used to identify and determine the exact nature and sequence of DNA in a sample. This was slow, laborious and expensive. The reason why DNA-chips are becoming the favourite tool of researchers in molecular biology is that not only is it fast, but, it’s also inexpensive, relatively easy to carry out in the fields and yields a massive amount of information on a large number of genes simultaneously in a short period of time.
Use of DNA-chips
The concept of DNA-chips is a new one but has already proved its worth in a number of various applications. They are used to detect gene mutations which can act as risk factors for many notable neoplastic diseases including breast and prostate cancers. With the help of technique, analysing the expression of the host cell DNA and RNA, effects of different treatments and medications on a specific disease condition could be adequately determined.
By detecting DNA from a large number of possible micro-organisms, it can also be used to determine the safety level of drinking water. With DNA-chips, a large number of these organisms may be tested for at the same time and would spare the laborious work of detecting each and every single organism separately.
What can we expect in the future?
With the identification of the entire human genome, the role of DNA-chips is becoming even more pivotal as a faster and more efficient technique is needed to sort out and sequence all the genetic data revealed by the Human Genome Project. The added qualities of portability and efficiency may, in the coming years, result in its use as a routinely used medical technique in clinics and out-patient-departments resulting in adequate and more effective treatment of patients presenting with a wide spectrum of conditions.