Chapter 2, Section 3
Stage 1: Interphase
How do little pigs get to be big pigs? Their cells grow and divide, over and over. The regular sequence of growth and division that cells undergo is known as the cell cycle. During the cell cycle, a cell grows, prepares for division, and divides into two new cells, which are called “daughter cells.” Each of the daughter cells then begins the cell cycle again. You can see details of the cell cycle in the diagrams. Notice that the cell cycle is divided into three main stages: interphase, mitosis, and cytokinesis.
The first stage of the cell cycle is called interphase. Interphase is the period before cell division. During interphase, the cell grows, makes a copy of its DNA, and prepares to divide into two cells.
Growing
During the first part of interphase, the cell grows to its full size and produces structures it needs. For example, the cell makes new ribosomes and produces enzymes. Copies are made of both mitochondria and chloroplasts.
Copying DNA
In the next part of interphase, the cell makes an exact copy of the DNA in its nucleus in a process called replication. Recall that DNA is found in the chromatin in the nucleus. DNA holds all the information that the cell needs to carry out its functions. Replication of DNA is very important, since each daughter cell must have a complete set of DNA to survive. At the end of DNA replication, the cell contains two identical sets of DNA. You will learn the details of DNA replication later in this section.
Preparing for Division
Once the DNA has replicated, preparation for cell division begins. The cell produces structures that it will use to divide into two new cells. At the end of interphase, the cell is ready to divide.
