One fertilised human cell divides just 47 times to produce over 100 trillion cells, which make up the remarkable human body. Each cell contains nearly two metres of DNA molecule threads (that's about 20 million km in all). Each DNA molecule has about three billion pairs of four types of molecules called bases. The sequence of these pairs is the genetic code that determines what our body is like. It's the same for all living beings, in different orders of complexity. In a gigantic exercise spread over years, ending 2000, the complete sequence of human DNA (genome) was worked out. Tweak the DNA and you get a different result. That's what happens in nature, which is why there are so many different life forms, surviving by adaptation. But humans have also been altering genetic codes to serve their own ends. Genetically modified (GM) plants, like Bt brinjal or cotton, are examples. The changed gene makes them resistant to some pests and drives up productivity. But protests against ‘Frankenstein food' have kept pace with advances in gene technology.
Genetic engineering - inserting new genetic sequences into viruses, bacteria, plants and other animals - has seen a worldwide explosion of biotechnology. On the one hand, human genes are studied to locate abnormalities, which cause disorders or make an individual more susceptible to various diseases. Switching that gene off can affect the onset of the disease. Conversely, vaccines use genetic pieces of a deadly microbe, like polio, to trigger the body's immune system and protect itself against attack.
Recent discoveries show that RNA (ribonucleic acid), the single strand cousin of DNA, plays an important role in making proteins. This has led to an alternative way of tweaking the genetic code, by silencing selected genes with RNA. This has dramatic potential for application in modifying plant genes for beneficial purposes.
Nobel Prize winner Phillip Sharp, formerly at the Massachusetts Institute of Technology, told TOI-Crest, "Almost all diseases can be described as a product of the normal or abnormal functioning of specific genes. The ability to silence these specific genes by design of small interfering RNAs opens a new approach to the treatment of a vast number of diseases."
Scientists at the J Craig Venter Institute are working on sequencing and analysis of disease-causing microbes such as anthrax and the mosquito species that carry yellow fever and malaria, and various strains of influenza and corona-virus. This, too, could help in developing new vaccines and treatments.
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