Cell Cycle And Cell Division

Introduction:

All living organisms start their life journey from a single cell. A single cell grows to form multiple cells, thereby including all microorganisms. Initially, the cells reproduce into two cells. The process continues when parent cells give rise to daughter cells every time they divide. The two new daughter cells can grow by themselves, divide further, and develop more cells, increasing the cell population. 

The cell population increases with the growth and division of the parental cell and its progeny. Thus, a single cell gives rise to other cells and forms a structure of millions of cells, resulting in organisms. The sequence of events that makes the cell eventually divide into two daughter cells is called a cell cycle, and the phase that the cells go through is cell division. Today, in this article, we will be talking about the Cell Cycle and Cell Division, Phases of the Cell Cycle, Cytoplasm division, and more. Make sure you stick by us till the end. So, without any further ado, let’s dive directly into it!

What Are Cell Cycle And Cell Division?

During cell division, DNA replication and cell growth happen in cells. The entire process of cell division, involving DNA replication, cell growth, correct division, results in progeny cells that contain intact genomes. The sequential event where the cell divides into daughter cells to constitute millions of cells is called the cell cycle. Hence Cell Cycle and Cell Division are essential processes in all living organisms.

Phases Of Cell Cycle:

The duration of the cell cycle varies based on organisms and cell types. There are two primary phases of the cell cycle.

  1. Interphase

  2. Mitosis phase 

Interphase:

The phase between two successive Mitosis phases is called Interphase. It takes only one hour in the 24-hour average duration of a human cell cycle. The Interphase lasts for nearly more than 95% of the cell cycle duration. Interphase is called the resting phase as the cell prepares itself for dell division & for undergoing cell growth and DNA replication in a sequential manner. 

The Interphase is further divided into three sub-phases – G1 phase (Gap 1), S phase (Synthesis), G2 phase (Gap 2). During these phases, the cell grows, DNA replicates in the nucleus, centriole duplicates in the cytoplasm, and proteins get synthesised and remain metabolically active. 

Mitosis phase:

Mitosis or actual cell division occurs in this phase. Nuclear division happens in this phase, where daughter chromosomes are separated. This is called karyokinesis and eventually results in cytoplasm division called cytokinesis. The components of the cells get reorganised in this phase. This phase involves four stages of nuclear division – Prophase, Metaphase, Anaphase, Telophase.

  • Prophase:

    This first stage of karyokinesis of mitosis occurs after the S and G2 phases of interphase. New DNA molecules formed are condensed with chromosomal material in this phase. Compact mitotic chromosomes are formed. Chromosomes are composed of two chromatids at the centromere, which undergoes duplication. 

  • Metaphase:

    In this phase, the centromere holds two sister chromatids. Kinetochores, small disc-shaped structures, are formed at the surface of the centromeres. They are attached to the chromosomes through the spindle fibres. Later, the chromosomes get aligned through spindle fibres to both poles of the spindle equator.

  • Anaphase:

    Chromosome split simultaneously to two daughter chromatids or daughter nuclei. In this phase, the centromeres split and the chromatids separate. Chromatids start migrating towards the two opposite poles.

  • Telophase:

    chromosomes lose their individuality in this phase. Individual chromosomes can no longer be seen and cluster at opposite spindle poles. They form discrete elements. Chromosome clusters are covered by a nuclear envelope, where two daughter nuclei are formed at each pole. Golgi complexes, endoplasmic reticulum, nucleolus develop at this stage. 

Cytoplasm Division – Cytokinesis:

  • Cell Cycle and Cell Division are completed in human cells as the cell divides into two daughter cells by the division of cytoplasm called cytokinesis.
  • In animal cells, furrow appears in the plasma membrane, which deepens, dividing the cell cytoplasm into two and later joining the centre.
  • In-plant cells, wall formation starts in the centre of the cell. This later grows outwards, which meets the lateral walls. New cell walls form, and in between the new walls, two adjacent cells are formed. The cytoplasmic division occurs where mitochondria and plastids are distributed to the two daughter cells. 

MEIOSIS: 

In Meiosis, cell cycle and cell division happen when a single cell divides twice. It produces four cells containing half the amount of genetic information that was originally contained. Hence, one meiosis cell divides twice, resulting in four daughter cells. These are the sex cells in humans – sperm in males and eggs in females. The key features of the meiosis process are as follows:

  • In meiosis, nuclear division (Meiosis I) and cell division (Meiosis II) occur, accompanied by a single cycle of DNA replication.
  • Homologous chromosomes are paired, and a combination happens between non-sister chromatids.
  • In Meiosis I, identical sister chromatids are generated after the parental chromosomes replicate during the S phase.
  • Four haploid daughter cells are formed in the meiosis II cell division phase, which completes the Cell Cycle and Cell Division process. 

Conclusion:

You now can understand the difference between a cell cycle and cell division. A cell has a series of phases that it has to undergo in a cell cycle and in cell division. The series of phases helps the cell split and increase in number. Cell cycle and cell division study material will enhance your knowledge and develop your learning towards cell division related to the cell cycle and the time taken by cells to replicate.

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