When you’ve doubled your genes, what’s 1 chromosome more or less?

ChomosomesAn individual with Down syndrome and a male calico cat have one thing in common—each has an extra chromosome. For animals, most instances of an extra chromosome result in birth defects or even death, but plants are another matter entirely. Many plants are able to survive the presence of an extra copy of their entire genome (known as polyploidy) and are often even more vigorous as a result. For plants, the process of polyploidy often results in a new species, making it an important mechanism in evolution. In fact, over 80% of plants may be a product of polyploidy.

However, this extra set of chromosomes can sometimes cause confusion during meiosis, the process by which sets of chromosomes are divided up to produce egg and sperm cells, with half the number of chromosomes present in a mature plant. Many recent studies have examined the effects of polyploidy on meiosis. A recent study by Drs. Andreas Madlung, Kirsten Wright, and J. Chris Pires, published in the September issue of the American Journal of Botany (www.amjbot.org/cgi/content/full/96/9/1656), examines the effects of polyploidy on a more common type of cell division, mitosis—the process of cell division that results in daughter cells that are identical to the parent cell—which allows the plant to grow and develop.

"We had been working on genomic responses to allopolyploidy for many years in newly formed allopolyploids and had noticed some instabilities during meiosis and gamete formation in newly formed allopolyploids," Madlung said. "The commonly held belief is that in established allopolyploids, incompatibilities of the two parental genomes somehow are reconciled during the evolution of the allopolyploid species but there is only relatively little data in the literature that supports this notion.

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