ient. It was anticipated however, that technological developments would lead to considerable reductions in costs and more efficient sequencing. The sequencing of the human genome at that time seemed an immense challenge because there was so little experience in sequencing large genomes. All that has changed, and some very large genomes have already been sequenced (Fig 13.4). There have been no significant changes in the sequencing technology; the dideoxy sequencing approach invented by Fred Sanger and his colleagues at Cambridge, UK, more than 20 years ago is still used. Instead, efficiency gains have been made through the use od automated fluorescence-based systems and capillary gel electrophoresis.While the first few years of the human genome project were devoted to producing high-resolution genetic and physical maps, large-scale human genome sequencing is now very much underway and 10% of the human genome has been sequenced by May 1999 (fig 13.5, electronic ref 3). Funded largely by the welcome trust, the greatest single contributor has been the Sanger Centre at Hixton, UK (fig 13.6). By May 1999 the Sanger centre had contributed over 100 Mb of finished human sequence (out of a global 300 Mb), and had also achieved a further 65 Mb of unfinished sequence (those sequences which have not yet been compiled into large contigs). In order to avoid wasteful duplication of effort, the HUGO-sponsored Human Genome Sequencing index identifies priority chromosomes or subchromosomal regions targeted by individual sequencing centres (electronic ref 4). Currently, chromosome 22 is set to be the first human chromosome to be completed. (fig 13.7).Partly in response to competition from the private sector (box 13.2), the UK Welcome Trust and the US national Human research Institute have collaborated to bring forward the timescale for completion of the Human Genome Project. The aim is to produce a working draft, comprising about 90% of the human genome, ...
