AAT Bioquest

What are the phases of a cell cycle?

Posted September 16, 2022


A cell cycle involves a series of events that occurs in the cell as it grows, develops, and divides. The cell cycle can be divided into 2 main phases: Interphase and M phase or Mitotic phase. 


Interphase is known as the resting phase or preparatory phase of the cell cycle. During this phase, the cell grows and replicates its DNA in preparation for division. 

Interphase is divided into three phases: 

  1. G1 phase or Gap 1, in which the cell grows and functions normally without replicating its DNA. 
  2. Synthesis or S phase, in which DNA synthesis begins. Although DNA is replicated during this phase, the number of chromosomes remains constant. 
  3. G2 phase or Gap 2, in which the cell continues growing as it prepares for division. 

Mitotic or M Phase

During this phase, the cell reorganizes itself completely. It takes place in two distinct stages of cell division – mitosis and cytokinesis. 

In Mitosis, the strands of DNA become tightly packed into a condensed form with each original DNA strand attached to its copy at one place. The membrane surrounding the nucleus then breaks down, followed by the chromosomes lining up along the center of the cell. The original DNA strand and its copy separate and move to opposite sides of the cell. 

Cytokinesis begins just as mitosis ends with a little overlap. In this stage, the cell membrane starts pinching inwards at the center line, separating the DNA into two sets, and cleaving the cytoplasm completely to form two new cells. The two newly formed cells are identical to each other and to the parent cells.

Additional resources

Cell cycle checkpoints

Cell Cycle Assays

Cell Navigator® CDy6 Mitosis Imaging Kit

Cell Meter™ Fluorimetric Live Cell Cycle Assay Kit *Optimized for 405 nm Violet Laser Excitation*