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Why won a human limb grow back if its cut off?

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Why won a human limb grow back if its cut off?

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In all mammals, limbs development from the “limb bud” is controlled by a series of genes which are only active during embryological development. At the point that the complete limb is present, these genes are shut off, and a new series of genes take over which controls cell division in a slightly different way, to expand and lengthen the areas of differentiated cells which are already present. These control growth through infancy and childhood and into adolescence. However, around the time that the body’s hormones signal maturity, even these genes are shut down, and then the only genes available to direct growth are the ones that we normally use for healing wounds. These are capable of sealing up cuts and growing new skin, repairing damaged muscle cells, re-establishing intact bone across a break, and things like that — but we no longer have the pluripotent undifferentiated stem cells which would move out to form all the tissues of a limb from new, and the genes which would control an

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