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Saturday, June 14, 2014

The Cell Cycle

Cell Cycle 

Cell Cycle is the process by which a cell and its contents divide, to give rise to two daughter cells and this process is known as mitosis.


 The Cell Cycle describes the different phases through which the cell divides. Cell cycle occurs through 4 different phases. These are

cell cycle Phases


  • G1 Phase
  • S Phase
  • G2 Phase
  • M-Phase
 The two major events occurs during cell cycle is the DNA synthesis and the chromosome segregation. DNA synthesis occurs in the S-Phase of the cell cycle; in this step the entire DNA (genetic content) of the cell is replicated. In M-phase or the mitotic phase chromosome segregates.

Between the S-Phase and M-Phase there are two checkpoints or Gap Phases namely G1 and G2 Phases. These are the checkpoints or error check phases where the cell confirms the proper replication of the DNA and the energy requirements are met to proceed to the next phase.

Cell Cycle - S-Phase

The major events that occur in the S-Phase or Synthesis phase of the cell cycle are

  • DNA Replication and
  • Sister chromatid cohesion
 DNA replicates and gives rise to chromatids and a pair of chromatids are called sister chromatids, these are held together by a protein called cohesin and the process is called as sister chromatid cohesion.

Cell Cycle - M - Phase

After the DNA replication process, the cell enters the checkpoint G2 Gap Phase, where necessary error checks are done and proceeds for the M – Phase or the mitosis phase. During the M-Phase the sister chromatids moves to the poles of the cells and the cell divides. Each daughter cell receives the identical genetic material.

Mitosis Phase – Overview

Mitosis Phase of cell cycle occurs through 4 different phases:


  • Prophase
  • Metaphase
  • Anaphase and
  • Telophase      

Mitosis

Prophase - Key Events
  • Chromosome Condensation
  • Nuclear Membrane Breaks
  • Microtubule organizers moves to the poles
Metaphase -  Key Events
  • Attachment of Microtubule to the centromere
  • Chromosomes are arranged to the center of the cell
Anaphase -  Key Events
  • Microtubules pulls the chromatids to the poles
Telophase -  Key Events
  • Nuclear membrane formation around the chromosomes
Cell divides by process called cytokinesis, where the cytoplasm of the two cells physically separates giving rise to 2 daughter cells.

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