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For many years, biological scientists have sought to decipher

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May29-14, 09:15 AM
P: 55
For many years, biological scientists have sought to decipher cellular function by quantifying the degrees of protein and mRNA expression within populations of their cells of interest. Classically, these measurements required combining many cells into a single sample and rupturing their membranes, thus exposing pooled quantities of the target molecule for detection. One limitation of these techniques is the reliance on average measurements: it is impossible to distinguish a uniform population of cells expressing intermediate quantities of a molecule from a population composed of separate low and high expressers. The distinction has proven to be important, particularly in the context of drug targeting of cancer cells; prescribing a dose to hit the “average” cell may completely miss the more aggressive “one percent.”

Could someone please explain what is being said by the bold and red part?
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May29-14, 07:42 PM
P: 1,502
Red part
A cell has a membrane to hold all the good parts inside - the nucleous, the mitochondria, the fluid, the vacules, just to name a few of the things inside a cell - to seperate the inner workings of the cell from the outside environment. You can simply think of it as a balloon analogy - if the balloon rupture ( breaks ), the stuff inside the cell can now be accessed some what easier by the person doing an experiment.

The black part
If many cells are ruptured, all of the ruptured cells will contribute their molecules ( from the interior of the cell ) for an experiment. Target molecule means a certain type of molecule will be selected for study.

Just as much as every person has a different shoe size, or weight, or height, with an average value being determined from measuring many people, the writer is stating that the individual cells may have different concentrations of the molecules within them. For the cells, the average concentration can be ascertained by measuring the pooled value from many cells, rather than mearuring each individual cell. But some cells may have higher concentrations, some lower than the average.
May29-14, 09:45 PM
Other Sci
Sci Advisor
P: 1,403
A useful analogy is to think of what would happen if an alien were studying humans the way biologists study cells. The alien would take thousands to millions of people, break them apart into their different components that all get mixed together before they can be measured. In most cases, this can give you a good idea of what composes the sample being studied. For example, if you put one million humans into the analysis machine, it would find one million brains, two million eyeballs, and ten million fingers. From this you could correctly conclude that each individual human has one brain, two eyes, and ten fingers. However, you would also count one million testicles and one million ovaries, so from this data you would also be tempted to conclude that each human has one testicle and one ovary. While it is true that human have on average one testicle and one ovary, the average nevertheless does not properly describe any individual in the population.

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