Introduction to the Cell Cycle

What you’ll learn to do: Identify the stages of the cell cycle, by picture and by description of major milestones

The cell cycle is an ordered series of events involving cell growth and cell division that produces two new daughter cells. Cells on the path to cell division proceed through a series of precisely timed and carefully regulated stages of growth, DNA replication, and division that produces two identical (clone) cells. The cell cycle has two major phases: interphase and the mitotic phase (Figure 1). During interphase, the cell grows and DNA is replicated. During the mitotic phase, the replicated DNA and cytoplasmic contents are separated, and the cell divides.

The diagram shows Mitosis and cell division as a cyclic process. The cycle starts at interphase. Interphase is divided into three stages: G1, S, and G2. During interphase, the cell is preparing to divide; DNA is duplicated, creating sister chromatids. Interphase is followed by the mitotic cycle, mitosis and cytokinesis. Mitosis is a process in which a diploid cell nucleus divides itself (duplicates) into 2 diploid nuclei. The first stage is prophase, during which the nucleus begins to disappear. The next stage is metaphase. During this phase, all sister chromatids are aligned in the center of the cell. Next is anaphase. During this phase, the sister chromosomes are all split. Next is telophase. A new nucleus is formed around each set of chromatids. The two nuclei are divided from each other, creating two new cells in a process called cytokinesis. Each new cell is now ready to being the cycle again.

Figure 1. The cell cycle