Medical geneticists have been claiming that all diseases, whether inherited or infectious, have genetic roots. The causal link, as far as the former category is concerned, is pretty clear. Sickle cell anaemia, for instance, is a disease that is inherited and is caused by a defective amino acid in one of the chains that constitute the globin protein of haemoglobin in our blood. The error is caused by a mutant gene supposed to code for the correct version of the protein. Other such diseases include thalassemia, muscular dystrophy, haemophilia and neurodegenerative afflictions like Alzheimer's and Parkinson's diseases.
What slightly complicates things is the second category of diseases. These afflictions are the result of environmental factors like carcinogens, diet and so on. But the probability of individuals getting the diseases depend on their respective genetic predispositions to these external assaults. Cardiac ailments, cancers and diabetes belong to this category.
In a particular kind of heart disease, there is supposedly a gene that produces an enzyme for cleansing blood vessels of excess cholesterol. When this gene malfunctions, the person is more likely to suffer from heart diseases-his diet and other habits only setting the chain with kinks in motion. The same is true for cancers. The presence of a mutant gene/s (not identified for sure yet) in such instances interferes with the cell's normal cell-division cycle, kick-starting an unstoppable division of cells.
Gene therapy, therefore, is all about trying to eliminate disease-causing errant genes or replacing them with their correct versions. It's also about introducing other genes which counteract their deleterious functioning.
The most difficult obstacle being faced in this area is that of gene delivery. For the right fragment of DNA to home in on the right point on the chromosome, many delivery vehicles are being tried. Viruses are one of them. Researchers use scissors-like restriction enzymes to snip away the harmful part of the viral genes and replace it with the pertinent fragment of human DNA. True to its properties of infection, the virus will copy its genes into the human DNA in the cells and multiply. So, the correct version of the DNA that's been dispatched is also copied.
However, the delivery viruses face the danger of being destroyed by the body immune system which identifies them as germs. Therefore, the next generation of delivery vehicles are fat bubbles. DNA fragments trapped in these bubbles are dispatched. The bubbles will not be identified as germs and destroyed. They also find it easier to merge with the membrane of the targeted cell and deliver the DNA inside it.
But more than all this, it's the yet unachievable and fantastic spin-offs which are all set to boggle the brain. Once all the human genes have been read, it will become easy to diagnose genetic predisposition to diseases. And then drug design can be customised to the genetic profiles of respective patients. But therein hangs an ethical tale.
