MADISON This week, scientists are revealing the genetic instructions inside corn, one of the big three cereal crops. Corn, or maize, has one of the most complex sequences of DNA ever analyzed, says University of Wisconsin-Madison genomicist David Schwartz, who was one of more than 100 authors in the article in the journal Science.
"The maize genome is a true maze full of confusing repeats and dead-ends that have troubled would-be sequencers for years," says Schwartz.
Publication of the genome is expected to advance knowledge of corn's ancestry, and also guide breeders trying to extract even more productivity from a crop that is expected to produce more than 200 million tons of grain from more than 87 million acres in the United States this year.
Producing the genome sequence required input from a unique optical mapping facility in the Laboratory for Molecular and Computational Genomics at UW-Madison.
Unlike traditional gene sequencers, who examine DNA letter by letter, the optical mapping system looks at bigger pieces, and that has positioned the lab's research as a key complementary component for working with the data produced by gene sequencers.
The first step in optical mapping system is to stretch out long, string-like DNA molecules and stick them to electrically charged glass plates. These molecules are sliced up into a series of consecutive chunks, marking them in the same way as a grocery bar code, and then painted with a fluorescent dye.
When the bar-coded molecules are exposed to a blue laser, the amount of fluorescent light they emit reveals the length of each barcode feature. The microscopes in the optical mapping system are fully automated, so millions of bar-coded molecules can be pieced together to reveal the structure of a genome.
The optical map supplies a scaffold, or big-picture view, of the structure of the DNA under study, says Schwartz. "Traditional sequencing must w
|Contact: David C. Schwartz|
University of Wisconsin-Madison