When genes fly off the handle

The deadly SARS virus sweeping the globe may have its origins in a very simple and often benign natural process of genetic mutation.


    Doctors and researchers are pulling their hair and biting their nails trying to find the elusive, mystery virus behind the SARS epidemic.


    Initial findings suggest that the Severe Acute Respiratory Syndrome (SARS) is the result of a mutant gene – a coronavirus found in cattle that has mutated enabling it to lodge itself in human beings.


    Conventional  antibiotics and medicines are proving ineffective,  resulting in high fatalities among the infected.  The silver lining is that this is not the first, and definitely not the last time genes have mutated. And, sooner or later, a cure will be found.

    A biotech scientist
    grapples with the latest
    gene mutant challenge
    in SARS

    In nature, genes mutate all the time. Where it involves a disease carrying microbe the challenge becomes immense and urgent.


    In 1901, Hugo de Vries, a scientist, coined the word mutation to describe sudden and drastic alterations he observed in the hereditary material of a flower, the evening primrose. Mutations are chance changes in DNA. It's like making a spelling mistake. A different message gets copied into future generations of  DNA.


    How do mutations happen? Normally DNA is copied very, very  accurately. But occasionally a piece of DNA gets deleted, inserted  improperly, inverted, or damaged. Genes also can  mutate if exposed to radiation or toxins. In that case, the DNA gets damaged and can't be read, so it isn't copied properly.


    Mutant genes  produce a change in the structure of the proteins they make, affecting the individual.  In some cases, mutations help animals and plants survive. For example, during some time in history, a gene that determines the colour of Biston betularia, a moth found in Manchester, England, mutated from its normally light form to a darker form which helped the species escape predators. Gradually, the ones with the light form disappeared, spotted and eaten by hungry birds while the darker ones survived.


    Genes mutate naturally all the time. Some mutations become incorporated into the gene pool, especially if their environment is changing, as it did in the case of Biston betularia. Today, scientists also induce mutations using genetic engineering. A controversial practice, it is mainly done to enhance the yield of agricultural products and improve resistance to diseases.


    According to Bretty Finlay, a leading microbiologist quoted by the National Post, micro-organisms tend to download new "genetic machinery" from their environment the way people download music and information from the Internet. "They can basically download any sequence they want."


    The coronavirus (which causes the common cold) and the suspect behind SARS, is  believed to have done just that, moving from infecting animals in  China to invading human lungs in Toronto in a short time.


    Disease resistant


    Strains of genes that mutate are known to either make people resistant to certain kinds of diseases or make them susceptible. For instance, a mutated gene strain resulted in making a section of the population in Scotland more prone to having breast cancer than others in the  community.


    Researchers in St. Andrews university found out that a gene mutated in a person 300 years ago. This was carried down to the progeny. The defect in the genetic structure labelled BRCA1 and BRCA2 increased  chances of breast cancer. With this knowledge doctors tracked the genetic defect and managed to work out remedial measures.


    In another instance, using a mutant gene as the starting point, scientists at University College in London found out that human beings were cannibals several centuries ago.  The team led by John Collinge reported that the protective genes, called polymorphisms, were mutant versions of the prion protein gene  which are said to have caused two brain epidemics -   kuru and Cruetzfeld Jacob’s disease. These genes are also believed to have caused the human form of Cruetzfeld Jacob’s or mad cow disease.


    The mutated gene led the scientists to the startling discovery that the two brain-destroying diseases were caused by eating contaminated human brain. The mutation that occurred later on was nature’s way of protecting humans from the two diseases.


    This mutation, or "polymorphism," is reportedly found at a certain spot in the prion gene and is known as M129V. Among the Japanese and certain populations on the Indian subcontinent and East Asia, a similar polymorphism called E219K also shows resistance to prion diseases.


    The recent unveiling of the human  genome has opened up new vistas in the understanding of genes including the mutant varieties.  As Nobel Prize winner for medicine Sydney Brenner said: “it would soon be possible to put the genes of every person in the world into a test tube. But even if only 100 000 human genomes could be captured and analysed, our understanding of disease and human development would be greatly advanced.”



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