Interphase is when the cell mainly performs its “everyday” functions; for example, it is when
a kidney cell does what a kidney cell is supposed to do. On the other hand, mitosis is when
the cell prepares to become two cells. Some cells, like nerve cells, do not complete the cell
cycle and divide, while others divide repeatedly.
Most of the cell cycle consists ofinterphase,the time between cell divisions. During this
time the cell carries out its normal functions and prepares for the next stage. Interphase
can be divided into three stages: the first growth phase (G1), the synthesis phase (S),
and the second growth phase (G2). During the G1 stage, the cell doubles in size and
doubles the number of organelles. Next, during the S stage, the DNA is replicated. In other
words, an identical copy of all the cell’s DNA is made. This ensures that each new cell that
results after cell division has a set of genetic material identical to that of the parental cell.
DNA replication will be further discussed in lesson 3. Finally, in the G2 stage proteins are
synthesized that will aid in cell division. In the end of interphase, the cell is ready to enter
the mitotic phase.
Figure 5.2: The cell cycle is the repeated process of growth and division. Notice that most
of the cell cycle is spent in interphase (G1, S, and G2) (I). ( 2 )
During the mitotic phase, nuclear division occurs, which is known asmitosis. Alsocytoki-
nesis, the division of the cytoplasm, occurs. After cytokinesis, cell division is complete and
two genetically identical daughter cells have been produced from one parent cell. The term
”genetically identical” refers to the fact that each resulting cell has an identical set of DNA,