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Genetics: New find regarding how cells grow without division (polyploidy)

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Color-coded chromosomes

From “Growing Without Cell Division: Mechanism Responsible for Cell Polyploidy Pinpointed?” (ScienceDaily, Nov. 1, 2011), we

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 a lot 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.

This happens in non-plant life forms as diverse as humans and fruit flies, but is best known in plants.

“We mathematically modeled the behavior of molecules known to control this special type of cell cycle and the progression to polyploidy. We then made certain predictions about how these molecules were regulated during the endocycle that we tested in fruit flies.”

Duronio said the study demonstrated that genes turned on and off in a cyclical manner was important for cells to continue endocycling and become polyploid. “We showed that one particular perturbation, or mutation, of this mechanism blocked the ability of cells to do that.”

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