Any time a cell divides, it makes more DNA
for the new cell. So, when a starfish loses a
leg for example, it creates copies of its DNA
for each new cell that grows to replace it.
Any cell that exists makes itself according
to the instructions of its DNA. So, many
different genes are used to make new starfish
parts. For example, when regenerating part of
a digestive tract, the cells that are newly formed
will use the genes that correspond to making a
cell for the digestive tract.
Every cell contains the exact same DNA,
but just different parts of the blueprint are
used for each cell type. When the starfish
first loses a limb, it responds by releasing
growth hormones and what are called
"heat shock proteins." These trigger the
same genes that are used when the starfish is
first developing, and it reads the DNA blueprint
to decide what the new cells that form should
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