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Sci Tech
New insight into basic mechanism of evolution
THE BASIC cellular machinery that generates the genetic diversity central to evolution does not operate quite the way scientists have thought, says a team of Iowa State University plant scientists.
Their 10-year investigation of recombination events on a section of a maize chromosome showed that not all recombination occurs in genes and not all genes are active sites for recombination.
Their research was published in the Proceedings of the National Academy of Sciences. By advancing the understanding of recombination in plants, the Iowa State research could lead to more precise control of gene integration in both traditional and biotechnological methods of plant breeding.
"Our research certainly changes the way we look at how recombination occurs in complex genomes like those of crop plants," said Patrick Schnable, who led the research team. "Recombination is the grease that keeps the evolutionary machinery running. Without it, evolution slows down."
Recombination is a fundamental process of sexual reproduction. In maize, as in humans, chromosomes are shuffled or recombined during sexual reproduction.
The process, called crossing over, results in offspring with genes arranged in combinations that is different from those present in either parent.
It is an important means of producing genetic variation, which is the key to evolution. For many years, scientists thought that most recombination occurs within genes and that the non-genic regions of complex genomes are recombinationally inert.
Schnable also is director of the Centre for Plant Genomics and the Centre for Plant Transformation and Gene Expression at Iowa State.
The research team became interested in recombination in 1989, while studying the region in the maize genome from the a1 gene (anthocyaninless1) to the sh2 gene (shrunken2).
The a1 gene is involved in coding an enzyme that gives colour to ornamental corn. The Sh2 gene codes an enzyme that is involved in starch metabolism.
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