Cell Cycle: Definition, Phases, Examples, Diagram, Functions, structure

Irshad AnwarUpdated on 02 Jul 2025, 05:56 PM IST

The cell cycle is a step-by-step process by which a cell grows and divides to give rise to two daughter cells. This is important in an organism's growth, development, and repair. The major steps involved in the cell cycle include the interphase and mitotic phase. Other steps include G1, S, and G2 phases found in interphase. Cell cycle is a topic of the chapter Cell Cycle and Cell Division in Biology. This article includes cell cycle and cell division definition, phases, diagram and notes.

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What is a Cell Cycle?
Different Phases of Cell Cycle
Cell Cycle and its Regulation
Tips, Tricks and Strategies to Prepare Cell Cycle for Exams
Recommended Video for Cell Cycle

Cell Cycle

What is a Cell Cycle?

Cell cycle definition refers to a process in which one cell develops and divides into two daughter cells. It is divided into four phases namely G1, S, G2, and M.

G1 Phase: The cells grow as well as perform all their normal activities.
S Phase: Chromosomes replicate.
G2 Phase: The cell grows further and checks if it's ready for division.
M Phase or Mitosis: The cell divides its chromosomes and cytoplasm into two identical daughter cells.

Regulating the cell cycle is very important in ensuring that an organism in general grows, develops, and maintains health.

Cell division definition is the process by which a cell splits into two identical daughter cells, enabling growth, repair, and reproduction.

Also Read:

Different Phases of Cell Cycle

The cell cycle is a biological process with fundamental activity in the growth and division of cells. It consists of a series of well-defined phases that allow for the precise duplication and distribution of the cell's genetic material into two daughter cells. These phases involve interphase, in which the cell grows and replicates its DNA, and the mitotic phase, in which the cell divides. The proper regulation of cell division phases is important for developmental work, tissue repair, and the maintenance of genetic stability in organisms.

Interphase

Cells spend most of their time in interphase.
Cell performs its usual functions during this time.
In interphase cell grows in size and prepares itself for the next division.
Interphase is the most active phase of the cell cycle.
The interphase lasts more than 95% of the duration of the cell cycle.
It was earlier regarded as a resting phase because the metabolic activities performed by the cell were not visible under a microscope.

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Howard and Pelc classified interphase into three sub-stages:

G1 - phase (First Gap phase)

The cell increases in size, doubles its organelles (such as mitochondria and ribosomes), and accumulates materials that will be used for DNA synthesis.
Cells are constantly performing their normal daily functions, including communicating with other cells, secreting substances, and carrying out cellular respiration.

S - phase (DNA synthesis phase)

At the beginning of the S stage, each chromosome is composed of one DNA double helix.
Following DNA replication, each chromosome is composed of two identical DNA double helix molecules.
Each double helix is called a chromatid.

G2 - phase (Second Gap phase)

At this stage, the proteins that will be helpful during the cell division are synthesised.
For example, proteins that form microtubules will be synthesised.

M Phase

The M phase, or mitotic phase, is the important part of the cell cycle in which the cell undergoes division to give two genetically identical daughter cells. It comprises two central processes:

Mitosis

Mitosis is also called the equational division (because the daughter cells have an equal number of chromosomes as that of parents) and somatic cell division (because it occurs in somatic cells). Mitosis was first observed by Strasburger in 1875. The term mitosis was given by Fleming in 1882.

Different Stages of Mitosis are:

Prophase

During this stage the chromatin condenses and the chromosomes are visible.
The nucleolus disappears and the nuclear envelope fragments.
With the disappearance of the nuclear membrane, the centrioles migrate to the opposite end and the spindle formation occurs.
During late prophase or prometaphase, kinetochores appear on each side of the centromere.
The sister chromatids are attached to the so-called kinetochore spindle fibres with the help of the kinetochore.

Metaphase

Chromosomes become fully condensed and distinct.
Chromosomes move towards the equatorial plane of spindles or metaphase plates.
Chromosomes are arranged with their arms directed towards the pole and centromere towards the equator.

Anaphase

The centromere splits and the two chromatids of the duplicated chromosomes separate from each other.
Each chromatid now becomes a daughter chromosome.
Daughter chromosomes, each with a centromere and single chromatid appear to move toward opposite poles.
Anaphase is the shortest phase of mitosis.

Telophase

During this phase, the spindle disappears and new nuclear envelopes develop around the daughter chromosomes.
Each daughter nucleus contains the same number and kinds of chromosomes as the original parent cell.
The chromosomes become diffuse chromatin and nucleolus reappears.
It is followed by the division of the cytoplasm.

Cell Cycle Diagram

Stages of Mitosis

Cytokinesis

Finally, in the cell cycle and at the end of mitosis, cytokinesis is the process by which the cytoplasm of the parent cell divides into two daughter cells. Cytokinesis begins with the formation of a cleavage furrow in animal cells, in which a contractile ring forms just beneath the cell membrane and consists of actin filaments. As this furrow deepens, it will pinch the parent cell completely, dividing it into two cells with a nucleus in each.

In animal cells, cytokinesis occurs through the formation of the cleavage furrow.
The cleavage furrow represents the indentation of the membrane between the two daughter nuclei.
A band of actin filament called the contractile ring starts to form the circular constriction between the two daughter nuclei.
Due to the action of the contractile ring, the furrow deepens continuously and ultimately a cell divides into two daughter cells.
Cytokinesis in the animal cell occurs centripetally, that is, from the periphery to the centre

Cytokinesis in Plant Cells

In plant cells, the presence of a rigid cell wall prevents the furrow formation.
Therefore, in plant cells, a new cell wall is formed between the daughter nuclei to complete the cytokinesis.
Many Golgi vesicles and spindle microtubules arrange themselves on the equator to form phragmoplasts.
The membrane of Golgi vesicles fuses to form a plate-like structure called a cell plate.
Golgi vesicles secrete calcium and magnesium pectate.
The further cell plate is modified into the middle lamella.
In plants, cytokinesis occurs in centrifugal order (cell plate formation is from the centre to the periphery).

Cytokinesis provides that each daughter cell receives a complete set of organelles and cytoplasm; thus, the cell cycle is completed, and two daughter cells become produced one genetically identical to the other.

Cell Cycle and its Regulation

The regulation of the cell cycle is important so that faulty or compromised cells cannot divide.
There can be a mutation during DNA replication and other events of the cell cycle.
Therefore, there are checkpoints in the cell cycle that would check for errors stop the cell cycle if there is any fault and allow the cell cycle to continue if there is no fault.
There are three checkpoints in the cell cycle G1 checkpoint, G2 checkpoint and M checkpoint.

Tips, Tricks and Strategies to Prepare Cell Cycle for Exams

Here are some tricks to study cell cycle for exams:

Phases of the Cell Cycle

Mnemonic: "I Prefer Mitosis"

I - Interphase (G1, S, G2)
P - Prophase
M - Metaphase
I - Anaphase
T - Telophase
O - Cytokinesis

Subphases of Interphase

Mnemonic: "G1 is So Great!"

G1 - Gap 1 Phase (cell growth)
S - Synthesis Phase (DNA replication)
G2 - Gap 2 Phase (preparation for mitosis)

Order of the Phases

Mnemonic: "IPMATC"

I - Interphase
P - Prophase
M - Metaphase
A - Anaphase
T - Telophase
C - Cytokinesis

Key Events in Each Phase

Mnemonic: "Penny Makes A Terrific Coin"

P - Prophase: Chromatin condenses into chromosomes
M - Metaphase: Chromosomes align at the equatorial plane
A - Anaphase: Sister chromatids separate
T - Telophase: Nuclear membranes reform
C - Cytokinesis: Cytoplasm divides, forming two daughter cells

Mitosis vs. Meiosis

Mnemonic: "MITOSIS Makes Identical Twins, MEIOSIS Makes Unique Samples"

M - Mitosis: Produces two identical daughter cells
M - Meiosis: Produces four unique gametes

Also Read:

Meiosis I	Meiosis II
Difference Between Mitosis and Meiosis	Difference Between Karyokinesis and Cytokinesis
Eukaryotic Cells	Prokaryotic Cells

Popular Questions

Directions for question :

M/s Deloitte Touche Tohmatsu Limited, one of the top four audit and accounting firms in the world with headquarters at London, UK, and with an operational presence in 153 countries, hires Management Trainees (MT) from all the premier management institutes of India thrice every year, in the months of January, May and September.

Each new group of Management Trainees (MT) have to go through a four month rigorous training schedule, after which they have to pass through a test consisting of a written assessment and a case-analysis. The top hundred ranked Management Trainees (MT) based on the performance in the test are confirmed as Management Executives (ME). The rest are given the opportunity of undergoing the training for four months one more time along with the next batch of Management Trainees (MT) and then passing through the subsequent test consisting of the written assessment and case-analysis. The Management Trainee (MT) who fails to get confirmed as a Management Executive (ME) the second time is fired.

The scatter-graph below depicts the number of Management Trainees (MT) at Deloitte taking the tests from January 2020 till May 2022, and the vis-à-vis hired Management Trainees (MT) at Deloitte who were fired :

It is also known that for the month of September 2019 at Deloitte, 96 hired Management Trainees (MT) failed to be confirmed as a Management Executive (ME) the first time, and that 36 hired Management Trainees (MT) were fired.

Question :

In which test did the minimum number of Management Trainees (MT) get confirmed as a Management Executive (ME) in the second attempt ?

Option: 1

September 2020

Option: 2

May 2021

Option: 3

January 2021

Option: 4

January 2022

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Directions for question:

Two friends Moloy and Niloy passed out from the Purulia Institute of Science and Technology with B.Tech degrees in Mechanical Engineering, but even after a year placement was hard to find. So they decided to take the challenge head-on, came down to Kolkata, rented a garage space on Park Street, and having an affinity towards making people enjoy good food, started their firm named 'B.Tech Bread-Omlette Wala'.

They started with three items on the menu. One was the French Toast which could be prepared in 3 minutes. The second was the Egg Tortillas which took 15 minutes to prepare. Any one of Moloy and Niloy could prepare any one of them at a time. The third was the Egg Bhurji with French Fries. This however was prepared on an automated fryer which could prepare 3 servings at a time and took 5 minutes irrespective of the number of servings equal to or below 3. The fryer did not need anyone to attend to it, and the time to put in the raw ingredients could be neglected. So one could tend to the preparation of other items while the Egg Bhurji with French Fries were being prepared.

They wanted to serve the orders as early as possible after the order was given. The individual items in any order were served as and when all the items were ready, and the order was then considered closed. None of the items on the menu were prepared in advance in anticipation of future orders.

On the first day, 3 groups of customers came in and ordered at 6.00 pm, 6.10 pm, and 6.13 pm. The first order was for a plate of Egg Tortillas, two plates of French Toast, and three plates of Egg Bhurji with French Fries. The second order was for a plate of French Toast and two plates of Egg Bhurji with French Fries. The third order was for a plate of Egg Tortilla and a plate of Egg Bhurji with French Fries.

On the backdrop of the above information answer the questions given :

Question:

Assuming that the next customer's order could only be attended to when the previous customer's order was closed, at what time would the first customer's order be considered closed ?

Option: 1

6.15 pm

Option: 2

6.17 pm

Option: 3

6.18 pm

Option: 4

6.20 pm

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Directions for question :

Six sticks of equal lengths were kept in the vertical position in an empty flower-vase, to be arranged at the six corners of a regular hexagon. The two ends of each of the sticks were of different colours.

The top ends of the sticks were one of each of the following colours – Red, Cyan, Pink, Brown, Black and Green. The bottom ends were one of each of the following colours – Blue, Yellow, White, Orange, Purple and Grey. Both the sets of colours mentioned were in no particular order.

It was also known that :

a) The stick with the red colour was opposite to the stick with the blue colour

b) There were exactly two sticks whose both ends had colours whose names started with the same letter

c) The stick with the grey colour was adjacent to the stick with the white colour

d) The stick with the cyan colour was adjacent to both the sticks with the brown colour and the one with the blue colour

e) The stick with the purple colour was adjacent to both the sticks with the grey colour and the one with the green colour

f) The stick with the white colour was opposite to the stick with the green colour

Question :

What was the colour of the bottom end of the stick having brown colour at the top end ?

Option: 1

White

Option: 2

Yellow

Option: 3

Black

Option: 4

Grey

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Directions for question:

On the backdrop of the above information answer the questions given :

Question:

Assuming that the next customer's order could only be attended to when the previous customer's order was closed, at what time would the third customer's order be considered closed ?

Option: 1

6.28 pm

Option: 2

6.35 pm

Option: 3

6.38 pm

Option: 4

6.45 pm

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Directions for question:

On the backdrop of the above information answer the questions given :

Question:

Suppose Moloy and Niloy had decided to process multiple orders at the same time, however strictly prioritising a first come first serve basis, when would the second customer's order be considered closed ?

Option: 1

6.20 pm

Option: 2

6.18 pm

Option: 3

6.15 pm

Option: 4

6.12 pm

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Directions for question:

On the backdrop of the above information answer the questions given :

Question:

Suppose Moloy and Niloy had decided to process multiple orders at the same time, however strictly prioritising a first come first serve basis, when would the third customer's order be considered closed ?

Option: 1

6.22 pm

Option: 2

6.25 pm

Option: 3

6.28 pm

Option: 4

6.30 pm

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Directions for question:

On the backdrop of the above information answer the questions given :

Question:

A fourth customer comes in and orders two plates of French Toast at 6.24 pm. Suppose Moloy and Niloy had decided to process multiple orders at the same time, however strictly prioritising a first come first serve basis. For exactly how many minutes would one of the friends be idle from 6.00 pm till serving the last customer, assuming that the four customers were the only ones to have come in within the period being discussed ?

Option: 1

Option: 2

Option: 3

Option: 4

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Directions for question:

On the backdrop of the above information answer the questions given :

Question:

Had Niloy been absent on that day, and assuming that the next customer's order could only be attended to when the previous customer's order was closed, at what time would the fourth customer's order (refer to the previous question) be considered closed ?

Option: 1

6:38 pm

Option: 2

6:42 pm

Option: 3

6:47 pm

Option: 4

6:49 pm

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Directions for question:

The bar-graph given below shows the foreign exchange reserves of Nepal (in million Rupees) from 2014 to 2021. Answer the following questions based on the graph :

Question:

What was the percentage increase (rounded to the nearest integer, if deemed necessary) in the foreign exchange reserves in 2020 over 2016 ?

Option: 1 None

Option: 2 None

Option: 3 None

Option: 4 None

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Directions for question:

The Jadavpur University’s Prince Anwar Shah Road hostel consists of two large separate buildings, one for the ladies and the other for the gents, while having a common kitchen and dining hall. It is the hostel of the CS and the EEC department of engineering students of the university.

In recognition of the growing dissatisfaction and hence complaints among the inmates of the hostel regarding the menu served for dinner, the Dean of the engineering department, Dr Aparesh Sanyal, personally decided to investigate the matter. He set about collecting information about the preference of dinner among the inmates, separately from the gents and the ladies wing of the hostel.

Dr Sanyal was able to gather the following partial information :

Hostel inmates	Menu preference for dinner			Total
Hostel inmates	Egg Meal	Fish Meal	Chicken Meal	Total
Gents			20
Ladies				64
Total		60