By Dr Ananya Mandal, MD
DNA and molecular biology has advanced by leaps and bounds. It has found use in pharmacology, genetic engineering in disease prevention, in increasing agricultural growth, in detection of disease and crime (forensics) etc.
Some fields that have shown remarkable growth due to advances in DNA technology include:
- pharmacology and nanotechnology
- archaeology and anthropometry
DNA technology in forensics
DNA is unique. Because it is unique, the ability to examine DNA found at a crime scene is a very useful forensic tool. The common methods used to identify and describe the DNA profile includes - Restriction fragment length polymorphism (RFLP) and Short tandem repeat profiling (STR).
Restriction fragment length polymorphism (RFLP)
In RFLP, the DNA is cut into segments of varying lengths by an enzyme, then the segments are separated out on the basis of size using a technique called electrophoresis.
The DNA fragments of a particular length are transfered to a nylon membrane. They are matched up with radioactively labelled fragments of DNA in such a way that only fragments that are identical stick together.
The excess radioactive fragments are washed away and an x-ray of the remaining fragments taken.
Electrophoresis is essentially applying positive and negative currents to a gel base and letting the DNA migrate to the positive pole (since it is negatively charged). The labelled fragments separate out based on their size. This gives a picture of which of the labelled fragments.
Short tandem repeat profiling (STR)
Short tandem repeat profiling (STR) involves use of an enzyme to make many copies of a small section of the DNA. This section is then cut into pieces by another enzyme, and separated by electrophoresis. The fragments are then visualised with a silver stain, with the pattern of light and dark bands seen being characteristic for an individual.
DNA in bioinformatics
Over the last decades there has been rapid progress in the human genome project and biotechnologies. These advances result in many complex datasets associated with in depth knowledge, e.g., genome sequences of many species, microarray expression profiles of different cell lines, single nucleotide polymorphisms (SNPs) or mutations in the human genome, etc.
This has given birth to a new field of Bioinformatics and has vast utility in the pharmaceutical industry. The two exciting techniques that have come up include the genome sequencing technology and the DNA chip technology.
It is estimated that the human genome has about 30,000 genes, which, surprisingly, only account for ~3% of the genome. The expression of these genes, i.e., the amount of protein products to be made in a cell, is tightly regulated so as to meet the requirements of specific cells and for cells to respond to changes in their environment. A central goal of molecular biology is to understand the regulation of protein synthesis.
DNA contains a vast amount of non-coding and non-functional sequences. These remain switched off and contain mutated genes or those inserted from other organisms, e.g., viruses and bacteria.
Much of these DNA that were not coding for any proteins were till date termed “junk DNA”. Now, in a series of papers published in September in Nature (Scientific American is part of Nature Publishing Group) and elsewhere, the ENCODE group have found that there may be signals and switches present in this junk DNA. This has paved ways to discover human disease over ages.
DNA in pharmacology and nanotechnology
Three dimensional nanostructures can hold and release drugs and regulate protein-folding. These have a definite potential in gene therapy.
Gene therapy involves using tiny molecules that carry the corrective enzyme or medication to the exact defective gene and identify and correct it. DNA Nanotubes can be used in gene therapy. Usually viral DNA is used as the vehicle that goes and gets introduced into a foreign gene. This is called transfection.
DNA in archaeology and anthropometry
The analysis of DNA extracted from archaeological specimens can be used to address anthropological questions. This helps in tracking DNA evolution, migratory patterns and species evolution over the ages.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)