Mapping the genes

humans have finally become acquainted with themselves. Researchers have been able to crack the human genome. The interpretation of the genome -- identifying the genes, their functions and controls and how they relate to human physiology and disease -- involved deciphering billions of strands of deoxyribonucleic acid (dna), which are encoded instructions that specify a person. The new findings are a result of the first comprehensive analysis of the human genetic code. Two teams accomplished this task that cost about us $3 billion. The first team was of Celera Genomics, a private company based in Maryland, usa , and the other was an international collaboration of scientists led by Francis Collins, director of the National Human Genome Research Institute at the National Institutes of Health in Bethesda, usa.
The startling discovery The key finding of the project is that there are approximately 30,000 genes in human beings. This means that humans have only 300 more genes than a mouse. Researchers in the past had estimated the number to be 140,000. They also discovered that human genes have been derived directly from bacteria that infected human predecessors millions of years ago and left their microbial dna behind. The genome sequence shows that humans probably originated on Earth about 100,000 years ago, a very short time in evolutionary terms. The research proves that all human beings are 99.99 per cent similar. Another important fact revealed by the research is that sperms carry twice as many mutations as eggs. Therefore, men are the major source of genetic errors in offspring. They are the agents of change -- responsible for most of the evolutionary innovations.

One astonishing finding is that genes comprise just 1.5 per cent of our chromosomes while repetitive copies of "jumping genes", or transposable elements, constitute about half our dna. T hese have been termed as "junk" dna, which are scattered throughout the genome. They play an important role such as helping humans respond to stress. They may have also contributed towards human evolution. Other species seem to get rid of this junk dna more easily -- only three per cent of the fruit fly's genome consists of such sequences.
The implications The findings have come as a surprise to genetic researchers and to the belief that genes control many aspects of a person's life. "People think genes are an absolute cause of traits. But for this to happen humans should have more genes," said Craig Venter, head of the Celera team. The low number of genes discovered has led to some fascinating implications. One of them is that there is no genetic basis for racial discrimination as humans share 99.99 per cent of their genetic information. There is more variation within racial groups than between them.

The interpretation of the genome is expected to revolutionise the field of medicine. Scientists sifting through the newly unveiled genome with computerised search engines have already discovered more than 40 hitherto unknown disease genes, including the ones responsible for epilepsy, deafness, colour blindness and muscular dystrophy. Hundred others may be discovered in the next few years, speeding the development of new drugs and diagnostic tests. The research is also providing insight on long-standing questions. Why the human sense of smell is so limited compared to that of many other mammals? In the past 10 million years, pre humans lost more than half of the 1,000 olfactory genes that are involved in the process of smelling, apparently choosing to concentrate on vision and other senses instead.

The research also raised some intriguing questions: how humans have become so much more complex than other creatures when they just have few extra genes. Richard Myers of Stanford University says it is not the number of genes, but how humans use them that led to the differences. "A fine sports car and a junker may have the same number of pieces. The difference is the quality of parts and the sophistication with which we put them together," said Myers.

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