An international team of scientists, including biologists from the University of North Carolina (UNC) at Chapel Hill, may have pinpointed for the first time the mechanism responsible for cell polyploidy, a state in which cells contain more than two paired sets of chromosomes. When it comes to human chromosomes and the genes they carry, our tissue cells prefer matched pairs. Bundled within the nucleus of our cells are 46 chromosomes, one set of 23 inherited from each of our parents. Thus, we are known from a cellular standpoint as "diploid" creatures. But a cellular chromosome situation common in plants and in many insects is polyploidy, in which there are more – sometimes many more – than two sets of chromosomes. Here, growth occurs through an increase in cell size versus an increase in cell number via cell division (mitosis). This allows more DNA to be crammed into the cell nucleus. Polyploidy also appears in some tissues of otherwise diploid animals, including people – for example, in specialized organ tissue such as muscle, placenta, and liver. These biologically highly active tissues also produce large polyploid cells. An intriguing slice of discovery science led by geneticist Dr. Bruce Edgar, of the University of Heidelberg, Germany, was published online on Oct 30, 2011 in the journal Nature. The research team may have identified for the first time the regulatory mechanism responsible for cell polyploidy. Study co-author Dr. Robert J.
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