Virtual map of the sheep genome: a world first
Australian research will allow sheep breeders to identify and select animals with superior traits more quickly
A team of international scientists, led by CSIRO and funded in part by AWI, has constructed a virtual map of the genome of the sheep.
The ‘virtual sheep genome' - a physical DNA map, which arranges more than 98 per cent of the sheep genome from the only eight per cent known of the sequence – has been made available by CSIRO. It contains the ‘best bet' about where the sheep's vast amount of hereditary information can be found on its 26 paired chromosomes.
The new sheep genome map will now fast-track the identification of the crucial genes responsible for sheep health and productivity, as well as for wool and meat quality. It is set to speed up the development of DNA marker tests, which will allow sheep breeders to more quickly identify and select animals with superior traits.
DNA marker tests will be particularly useful for determining parentage and positively identifying animals with traits that are difficult or expensive to measure in the live animal. They will also enable selection decisions to be made early in the animal's life since they only require analysis of a blood sample, which can be taken at any stage.
Dr Brian Dalrymple, a bioinformatics scientist from CSIRO Livestock Industries in Brisbane who leads the research, says his team drew on components of the $3 billion human genome project and also on work already done on the dog and cow genomes. CSIRO was also a partner in the US$53 million Bovine Genome Sequencing Project and has applied that expertise to the sheep.
"Internationally, there has been substantial genomics research undertaken on cattle, with a near-complete cow genome sequence now publicly available," Dr Dalrymple says. "The genes for sheep are similar to the genes for humans, the major difference being their order on the chromosomes.
"While the investment in sequencing the sheep genome will eventually be made, we have been very pragmatic and resourceful in the meantime. We have worked out how to leverage the investment in the other mammalian genomes to build a virtual genome around the small amount of existing sheep sequence."
This research has laid the groundwork for the eventual sequencing of the sheep genome itself. "We took the DNA sequences from the ends of 180,000 sheep DNA fragments called BACs (Bacterial Artificial Chromosomes - chromosomes that have been stored in bacteria), which covered the sheep genome about 12 times over.
"Then it was like a giant puzzle. We mapped the BAC-end sequences onto the frameworks of the human, dog and cow genomes. That honed the information down to 1172 sections of sheep genome, which we had to put together in the right order with the right orientation."
The virtual sheep genome has been made possible by SheepGenomics, a major $30 million joint initiative of Meat and Livestock Australia and AWI, which is supported by 11 leading research organisations in Australia and New Zealand. In turn, SheepGenomics is supporting the development of a range of sheep genomics resources by the International Sheep Genomics Consortium, a collaboration of scientists and funding agencies from Australia, France, Kenya, New Zealand, the UK and the US.
More information: Rob Forage, SheepGenomics program director, 02 9463 9169, rforage@sheepgenomics.com, www.sheepgenomics.com
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