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The Body Electric
erythrocytes, which still contained a nucleus, and possibly other cell
types.
The electrical forces turned the key that unlocked the repressed genes.
The exact nature of that key was the one part still missing from the
process. The current couldn't act directly on the nucleus, which was
insulated by the cell's membrane and cytoplasm. We knew that the
current's primary effect had to be on the membrane. The cell membrane
itself was known to be charged. Its charge probably occurred as a specific
pattern of charged molecules, different for each type of cell. We postu-
lated that the membrane released derepressors—molecules that migrated
inward into the nucleus, where they switched on the genes. Based on
recent findings about the structure of RNA, we suggested that the de-
repressor molecules might be a stable form of messenger RNA that per-
sisted in the mature red cell even after its nucleus shriveled up and
turned itself off. RNA molecules can be stable for a long time when they
are folded, the strands secured together by electron bonds. If such folded
RNA molecules were stored in the cell membrane, the tiny currents
could release their bonds and unfold them. This hypothesis has not yet
Fracture healing was ended by a straightforward negative-feedback
system. As the gap was filled in with new matrix, the
bone gradually
redistributed its material to balance the stresses on it from the action of