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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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.
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.
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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.
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.
Howard and Pelc classified interphase into three sub-stages:
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 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:
Cell Cycle Diagram
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
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.
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.
Here are some tricks to study cell cycle for exams:
Mnemonic: "I Prefer Mitosis"
Mnemonic: "G1 is So Great!"
Mnemonic: "IPMATC"
Mnemonic: "Penny Makes A Terrific Coin"
Mnemonic: "MITOSIS Makes Identical Twins, MEIOSIS Makes Unique Samples"
Also Read:
Meiosis I | Meiosis II |
Difference Between Mitosis and Meiosis | Difference Between Karyokinesis and Cytokinesis |
Eukaryotic Cells | Prokaryotic Cells |
This is to ensure that a cell grows, repairs or reproduces itself accurately.
The cell cycle is the series of events that cells undergo as they grow and divide. It includes phases such as interphase and mitosis, ensuring accurate replication and distribution of genetic material.
Checkpoints, cyclin-dependent kinases, and cyclins modulate the cell cycle at multiple stages.
The four major stages of mitosis are prophase, metaphase, anaphase and telophase.
If the cell cycle is not well controlled, cells can grow uncontrollably and lead to the formation of diseases such as cancer.
The cell cycle was discovered and clarified through key contributions by scientists Leland H. Hartwell, Paul M. Nurse, and Tim Hunt, who identified crucial regulatory molecules and won the Nobel Prize in 2001 for their work.
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