Page 130 - The Miracle in the Cell

THE MIRACLE IN THE CELL

Figure 7.1 A newly fertilized egg cell surrounded by sperm cells
might seem, because at some stage of the division process, some of the
copied cells receive a command to differentiate from their sister cells
and form completely different structures. With time, cells arising from
the same parent cell differentiate during the process of cell division to
form different tissues and organ systems. Some become light-sensitive
retinal cells, others liver cells, others nerve cells receptive to heat and
cold, and some become auditory cells sensitive to sound waves.
How does this division of labor come about? Since a cell cannot
decide on its own to become a retina, where does this decision origi-
nate?
The DNA or genetic information contained in all of these cells is

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