Scientists open first chapter of the book of life with decoding of human chromosome
An international team of researchers has passed a scientific milestone by deciphering, for the first time, the complete genetic code of a human chromosome and revealing the existence of hundreds of genes previously unknown in humans.
Reported in this week's edition of Nature (2nd December), researchers from the Wellcome Trust-funded Sanger Centre near Cambridge, Keio University in Japan and US laboratories at the University of Oklahoma and Washington University, St. Louis have succeeded in writing down the 34 million 'letters' that make up the entire sequence that contains all the protein coding genes of Chromosome 22. This is the first human chromosome sequence to be completed. It has revealed 679 genes, of which 55 per cent were previously unknown in humans, and improvements in software for finding genes may enable us to find even more. The work gives scientists a real insight into the way genes are arranged along a strand of DNA and how they might be controlled, paving the way for huge advances in medical diagnosis and treatment.
There are 23 pairs of chromosomes in the human genome. Each chromosome consists of a single linear molecule of DNA, which is composed of four chemical bases represented by the letters A (adenine), T(thymine), G (guanine) and C(cytosine). It is the order, or "sequence", and context of these letters which determines how our bodies are made, and our predisposition to certain diseases.
Previous research has already revealed that chromosome 22 is implicated in the workings of the immune system, congenital heart disease, schizophrenia, mental retardation and several cancers including leukaemia. The availability of the DNA sequence will revolutionise the future of research on these diseases, and the function of other genes on Chromosome 22.
The initiative forms part of the Human Genome Project; an international collaboration in which scientists at the Sanger Centre together with colleagues in the US, Japan, France, Germany and China are sequencing the entire human genome.
Work continues to complete the estimated 3 billion letters that make up the whole of the human genome, with a first working draft available by Spring 2000, and the highly accurate, finished form before 2003. One third of the genome has already been completed, most of which has been done this year, and the data has been deposited in public databases.
"This is the first time that we have been able to see the organisation of a chromosome at the base-pair level. This immediately suggests new experiments and avenues of research which can be pursued."
Dr Ian Dunham at the Sanger Centre who led the international chromosome 22 team
"For the first time the scientific world knows what a whole human chromosome looks like and the knowledge that we derive from this discovery will be used for centuries to come. It is a remarkable achievement that will change the way in which diseases and other medical conditions are diagnosed and treated in future."
Dr Michael Dexter, Director of the Wellcome Trust commented
The sequence of chromosome 22 includes 298 genes previously unknown in man, which are being released without the constraints of patents and fees. The fact that all of this information is now freely available for scientists to use, is of major importance, if the knowledge of our genetic make-up is to be used for the good of mankind.
"Until now, the ability to sequence an entire chromosome was just hypothetical. No one knew if there would be insurmountable problems that prevented the assembly. Having done this for chromosome 22 tells us we will be able finish the human genome in another two or three years."
Dr Francis Collins, Director of the National Genome Research Institute at the National Institutes of Health, the US partners in the publicly funded Human Genome Project