Intended for healthcare professionals


First human chromosome is sequenced

BMJ 1999; 319 doi: (Published 04 December 1999) Cite this as: BMJ 1999;319:1453
  1. Susan Mayor
  1. London

    The sequence of the first human chromosome to be decoded has been announced this week, with the publication in Nature of the DNA sequence for chromosome 22. The publication is the first milestone in the human genome project—a worldwide collaborative effort to decipher the complete genetic code. Chromosome 22 is the second smallest of the 23 human chromosomes.

    The information confirmed the efficacy of the sequencing methods. It also gave new information for locating genes associated with specific diseases and on how the chromosome evolved, with the finding of eight regions occurring in duplicate.

    Lead researcher Dr Ian Dunham, senior research fellow at the Sanger Centre, in Cambridge, said: “With the sequencing of chromosome 22, we have achieved the longest sequencing of DNA yet achieved in any organism. It will now be possible to identify candidate genes for diseases associated with changes to this chromosome.”

    The sequence has shown that at least 545 genes are encoded by the DNA in chromosome 22—although there may be as many as 1000 (Nature 1999;402:489-95). There are thought to be at least 27 human disorders associated with changes to genes on chromosome 22. Of particular interest are areas associated with schizophrenia and one form of spinal cerebellar ataxia.

    The next step is the sequencing of the entire genome, expected by spring 2000. Dr Peter Little, reader in molecular genetics at Imperial College of Science, Technology and Medicine, London, said: “For the first time, we will be able to identify the 200000 to 300000 proteins that make up a human being. Knowing the genome will force medicine to focus more on prevention and counselling than on treatment.”

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