Cell Cycle and Cell Division

Edited By Team Careers360 | Updated on May 11, 2022 03:22 PM IST

Cells divide and grow through a series of events known as a cell cycle. Cells spend most of their time in the interphase, during which they divide, grow, replicate their chromosomes, and prepare for cell division. At this point, the cell has completed its division, left interphase, and entered mitosis.

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The resultant cells, known as daughter cells, enter a new round of the cell cycle and enter into their own interphase.

Define cell cycle?

Cells divide and grow through a series of events known as a cell cycle

How does the cell cycle work?

A frog zygote was studied by Prevost and Dumas (1824) while they discovered the cell cycle. This is a series of steps a cell passes through in order to divide and produce new cells.

It is the entire process by which a population of cells grows and develops with the help of one single parent cell.

Mitosis

A eukaryotic cell divides into two distinct but similar nuclei during mitosis, the process in which DNA and chromosomes are separated. Mitotic spindles are specialised structures consisting of microtubules that separate chromosomes during mitosis.

Cytokinesis

In this phase, the cytoplasm of the cell divides. The process begins as soon as mitosis ends. A rigid cell wall and high internal pressure make plant cells much tougher than animal cells. As a result, animal and plant cells undergo cytokinesis at different times.

Phases of the Cell Cycle

During the cycle, a series of events take place within a cell to cause it to mature and divide. This process involves the replication of the genome and the synthesis of cell organelles, followed by cytoplasmic division.

An average human cell cycle lasts around 24 hours and is characterized by normal eukaryotic cell growth and division. However, the length of the cycle varies from organism to organism and is dependent on the type of cell.

Diagram of the cell cycle

Cell cycle

Stages of the cell cycle

During the process of dividing, a cell must accomplish a few important tasks: It must grow, duplicate its genetic material (DNA), and physically split into two sister cells. These tasks are performed in an organized, predictable manner by the cells, which is known as the cell cycle. Because the two daughter cells can start the exact same process over again from the beginning at the end of each round, the cell cycle is a cycle, not a linear pathway.

The stages of the cell cycle are divided into two major phases into eukaryotic cells or cells with a nucleus: interphase and mitotic (M) phase.

Cells grow and make a copy of their DNA during interphase.
Cells divide their cytoplasm and DNA during the mitotic (M) phase, resulting in two new cells.

There are two main phases in a typical eukaryotic cell cycle:-

Interphase cell cycle

Interphase is a phase in the cell cycle when the cell undergoes both cell growth and DNA replication in preparation for division. It occupies approximately 95% of the entire cycle. During the interphase, the following three phases occur:

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G1 phase of cell cycle (Gap 1):

The G1 phase consists of the time between the end of mitosis and the start of DNA replication during the S phase. During that time, certain intracellular components, including the centrosomes, are replicated, preparing the cell for DNA replication. Biologically, a cell must be ready to take on DNA replication before beginning the process. Cellular monitoring takes place during the G1 phase. This phase is characterized by metabolic activity and continued growth without replication of DNA.

Cells check the cellular environment and size during G1 to determine whether conditions support DNA replication. The cell leaves G1 only once it is ready to reproduce its DNA. The process of DNA replication can be paused during G1 if all cells are not ready. Cells can then enter the G0 phase. G0 can last for days, weeks, or even years, depending on whether a cell is ready to continue the cell cycle.

Phase S (Synthesis) - DNA replication occurs in this phase. When the initial amount of DNA in the cell is referred to as 2N, then after replication, it becomes 4N. Nonetheless, the number of chromosomes does not change, i.e., a cell with 2n chromosomes at G1 will continue to have 2n chromosomes at the end of the S phase. Into the cells that contain centrioles, the centriole divides into two centriole pairs.
G2 phase (Gap 2) - During this phase, the RNA, proteins, and other macromolecules needed for the multiplication of cell organelles, spindle formation, and cell growth are produced as the cell prepares to enter the mitotic phase.

Adult animals have some cells that do not divide and some that divide only to replace the damaged or dead cells. These cells include cardiac and kidney cells. If these cells fail to divide further, they move into an inactive G0 phase, which is also known as the quiescent phase. Cells that do not divide remain metabolically active but do not divide unless instructed to do so.

What is cell division definition?

It is a process by which a cell divides into daughter cells after distributing its genetic material and cytoplasm. The cell cycle is an important part of cellular reproduction and is an integral part of the larger cell cycle.

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Cell Division Importance:

Importance of Mitosis and Meiosis

Diploid daughter cells are usually formed during mitosis, resulting in identical genetic makeup.
Mitosis is responsible for multicellular organism growth.
Nucleus-cytoplasm ratios are disrupted by cell growth. The nucleus-cytoplasm ratio is restored by cell division.
Mitosis plays a crucial role in cell repair. A large number of epidermal cells, gut lining cells, and blood cells are constantly replaced.
Mitotic differences in meristematic tissues - lateral and apical shifts are responsible for continuous development during the lifespan of plants.
Meiosis plays an important role in plant development.
In sexually reproducing organisms, meiosis preserves the chromosome number of each species over generations.
Increasing genetic variation within an organism population from one generation to the next is also beneficial. Variations play a very significant role in evolutionary processes.

Diagram of the cell division

Cell Division

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Frequently Asked Questions (FAQs)

1. What do you understand about the cell cycle?

Cell cycle refers to the series of events that result in the duplication of the cell along with the DNA.

2. How many stages are there in mitosis?

During the cell cycle, there are four important stages:

1. Interphase

2. Prophase

3. Metaphase

4. Anaphase

5. Telophase

6. Cytokinesis

Of which, prophase, metaphase, anaphase, and telophase are 4 stages of M- phase.

3. The stages of a cell cycle are as follows:

Following are the phases of the cell cycle:

Phases including G1, S, and G2 are referred to as the interphase.
In the mitotic phase, there are prophases, metaphases, anaphases, and telophases.
Cytokinesis - The cytoplasm divides during this phase.

4. Who first discovered the cell cycle?

During the 19th century, Walther Flemming discovered the cell cycle. The professor at the Institute of Anatomy was responsible for this discovery.

5. How important is it for cells to divide?

Here are some reasons why cell division is critical:

Cell division promotes the survival and growth of organisms.
Maintaining the number of chromosomes.
Cell renewal in damaged tissues.

6. At what point in the cell cycle is the most important?

Cell division occurs during interphase. The cell stays in interphase for the longest time. Cells go through this phase to prepare for division. This is when the cell grows and replicates.