The full genome sequences of man and mouse will take some sorting out. One aim will be to ascribe functions to the thousands of genes discovered. But picking out genes in the scrambled, repetitive mess of many large genome sequences is tricky.
Researchers from an international consortium now announce the first chapter in one of the biggest efforts yet to pin down the purpose of mice genes: the Mouse Gene Encyclopedia Project
One way to identify and locate genes in the genome morass is to collect messenger RNA (mRNA) strands. These are produced when the instructions to make proteins carried in each gene are read.
DNA is made up of two bound strands of chemical 'bases', each represented by a letter (A, G, C and T). Bases always bind to the same partners, so mRNA strands complement the gene sequences they represent. Preparing and sequencing a new DNA strand that matches an mRNA template offers a replica 'clone' of that gene. This complementary DNA (cDNA) clone has a sequence identical to that of the original gene.
The research team, coordinated by Yoshihide Hayashizaki of the RIKEN Genomic Sciences Centre, Kanagawam, Japan, prepared and investigated a library containing some 20,000 of these mouse cDNA strands. The collection includes clones made using mRNA strands taken from various tissues at various stages of development.
The team tried to find out what the genes represented by these cloned strands do by comparing the DNA sequences with each other and with known genes in other species. The researchers found, for example, over a hundred new genes representing metabolic enzymes, and ten that seem very similar to genes causing human diseases.
"I think this is a very significant effort," says Robert Strausberg, who is developing similar collections of both human and mouse cDNA clones at the National Cancer Institute in Bethedsa, Maryland. "Full length cDNA libraries will provide the platform for much of the post-genome research such as proteomics."
Echoing the race to decode the human genome, two separate groups are also working on the mouse genome sequence. Private firm Celera looks likely to finish first, perhaps within the next few months. The second group, an international consortium of private companies and public research agencies set an original completion target of 2003, but hopes to finish sooner.