T.h.e.  G.e.n.e.t.i.c.  D.i.s.e.a.s.e.s

    Although scientists has got to know the mechanisms of single gene disorders through genetic mapping, the actual problem in society lies much more on the more common diseases such as heart disease and stroke.

    Over the last few decades, much effort has been put to characterise the environmental causes behind such diseases but few attempts have been made to identify their genetic basis. Recently the technology for identifying such genes has become available.

    The human genome is approximately 3.3 billion base pairs long and contains around 100,000 genes. The genes are responsible for specifying the protein molecule so as to define the organisation of cells. Yet identifying and understanding the function of genes that are involved in common diseases is one of the most challenging tasks that geneticists have to face. The number of genes involved in such conditions varies. It is thought that around six genes are responsible for regulating blood pressure. The question that lies in this topic is : How do the genes interact with each other and with the environmental factors?

    There is a hypothesis that helps us understand the interaction between the genes. Let us assume there are 6 genes that causes hypertension. If a person is born with all the 6 genes, then inevitably hypertension will result. On the other hand if a person is born with none of the genes, then even if he leads a very unhealthy lifestyle, he will still be spared from hypertension. Obviously, most people are born with 2 or 3 of such genes, and the environmental factor will no doubt affect the cause of hypertension.

     The heritability ratios of various common gene-related diseases have been estimated and they differ from one disease to another. For some common diseases such as strokes, it seems that environmental factors play a more significant role than genes in the development of such diseases.