Cell Cycle Phases in Order Explained

In this cell cycle phases in order explained post we have briefly explained about the cell cycle phases: Interphase and M (mitotic) phase.

The cell cycle phases is the sequence of events occurring in an ordered fashion which results in cell growth and cell division. A cell cycle is a set of events that occur in a cell as it divides and grows. A cell spends the majority of its time in interphase, which is when it grows, duplicates its chromosomes, and prepares to divide. After that, the cell exits interphase, goes through mitosis, and completes its division. The daughter cells that result go through their own interphase and start a new round of the cell cycle.

Cell Cycle

The Cell Cycle Phases

The cell cycle phases process through which cells multiply and divide into two new cells is known as the cell cycle. G1, S, G2, and M are the cell cycle phases

The Cell Cycle Phases


The cell goes through typical growth processes while preparing for cell division during interphase. Many internal and external parameters must be satisfied for a cell to transition from interphase to mitotic phase. G1, S, and G2 are the three stages of interphase.

G1 Phase

Because there is little change evident at the microscopic level, the initial stage of interphase is dubbed the G1 phase (first gap). The cell, on the other hand, is very active biochemically during the G1 stage. The cell grows and accumulates the components of chromosomal DNA and related proteins, as well as sufficient energy reserves, to accomplish the task of nucleosome replication.

The length of the G1 phase varies from cell to cell, but it is longer than the other three the cell cycle phases. The G1 phase accounts for 25-40% of a cell’s development period. Within the G1 phase, there is a precise check point at which DNA synthesis begins, and the cell proceeds to division once the biochemical steps associated with that moment have occurred.

S Phase

Interphase’s synthesis phase is biochemically a period of vigorous DNA and histone synthesis. DNA replication results in the production of two identical copies of each chromosome sister chromatid that are firmly connected at the centromere region during the S phase (synthesis phase).

DNA replication in the S phase produces identical pairs of DNA molecules, known as sister chromatids, which are firmly connected to the centromeric region. Each chromosome is made up of two sister chromatids and is a duplicated chromosome at this stage. During the S phase, the centrosome is duplicated. The mitotic spindle, which orchestrates the movement of chromosomes during mitosis, will be formed by the two centrosomes.

The centrosome is made up of two rod-like centrioles that are at right angles to one another. Centrioles aid in the organisation of cell division. Many eukaryotic organisms, including plants and most fungi, lack centrioles in their centrosomes.

G2 Phase

S phase is followed by G2. This phase accounts for 10 to 25% of the cell’s production period. The chromosome has two chromatids in the G2 phase, meaning the cell has twice the quantity of DNA.

To generate resources for the mitotic spindle, several cell organelles are replicated, and the cytoskeleton is disassembled. During G2, there may be increased cell proliferation. Before the cell may start the first stage of mitosis, the last preparations for the mitotic phase must be completed.

M (mitotic) phase

M phase follows G2 phase. During this phase, the cell divides into two daughter cells, each with an equal number of chromosomes. Following the M phase, the cell enters the G1 phase, and the cell cycle is repeated. However, some cells do not enter the G1 phase once mitosis is completed, and these cells are referred to as G0 cells.

Cell Cycle

The Cell Cycle Phases: M (mitotic) phase, Source : cyberbridge.mcb.harvard.edu


Mitosis is the process of separating the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells. Prophase is the initial phase of mitosis. During prophase, chromatin, a combination of DNA and proteins found in the nucleus, condenses.


The cell cycle’s metaphase occurs when all of the genetic material is condensed into chromosomes. Sister chromatids are chromosomes that have been replicated and remain connected at a central place called the centromere.


Anaphase is the fourth phase of mitosis, the process by which a parent cell’s replicated genetic material is separated into two identical daughter cells from the nucleus.

The mitotic spindle is a structure that separates the chromosomes. The mitotic spindle is made up of microtubules, which are long proteins connected to a chromosome on one end and the cell pole on the other.


The spindle fibres vanish, and the nuclear membrane reappears as chromosomes arrive at opposing poles and unravel into thin strands of DNA.


The final the cell cycle phases of mitosis overlap with cytokinesis, the split of the cytoplasm to generate two new cells. Depending on the cell, it can begin in either anaphase or telophase and stop shortly after telophase. When cytokinesis is complete, we have two new cells, each with a complete set of chromosomes that are identical to the mother cell’s.

Further Readings


  1. https://www.genome.gov/genetics-glossary/Cell-Cycle
  2. https://courses.lumenlearning.com/biology1/chapter/the-cell-cycle/
  3. https://www.nature.com/scitable/topicpage/eukaryotes-and-cell-cycle-14046014/
  4. https://open.umn.edu/opentextbooks/textbooks/biochemistry-free-for-all-ahern