By Ewen Callaway
The wheat genome is finally complete. A giant international consortium of academics and companies has been trying to finish the challenging DNA sequence for more than a decade, but in the end, it was a small US-led team that scooped the prize. Researchers hope that the genome of bread wheat (Triticum aestivum) — described in the journal GigaScience this month — will aid efforts to study and improve a staple crop on which around 2 billion people rely.
The wheat genome is crop geneticists’ Mount Everest. It is huge — more than five times the size of a single copy of the human genome — and harbours six copies of each chromosome, adding up to between 16 billion and 17 billion letters of DNA. And more than 80% of it is made of repetitive sequences. These stretches are especially vexing for scientists trying to assemble the short DNA segments generated by sequencing machines into much longer chromosome sequences.
It’s like putting together a jigsaw puzzle filled with pieces of blue sky, says Steven Salzberg, a genomicist at Johns Hopkins University in Baltimore, Maryland, who led the latest sequencing effort. “The wheat genome is full of blue sky. All these pieces look like a lot of other pieces, but they’re not exactly alike.”
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