Cell-Structure-And-Functioncell-Cycle-And-Cell-Division-1
Interphase:
The cell cycle is divided into Interphase and mitotic (M) phase.
Interphase, also known as resting stage, is divided into G1 (Gap 1), S (Synthesis) and G2 (Gap 2) phase.
During the G1 phase the cell is metabolically active and continuously grows. In S or synthesis phase DNA synthesis takes place whereas in G2 phase, protein synthesis occurs and the cell prepares itself for mitosis.
The amount of DNA per cell doubles during the S phase. However, there is no increase in the chromosome number. If the initial amount of DNA is denoted as 2C then it increases to 4C. However, if the cell had diploid (2n) number of chromosomes at G1, even after S phase the number of chromosomes remains the same, i.e., 2n.
Some cells, such as heart cells and cells that divide occasionally, do not divide further and exit the G1 phase and enter the G0 phase (quiescent phase). Cells in this stage remain metabolically active and start dividing as per the requirement of the organism.
Mitotic phase:
Mitotic phase consists of karyokinesis which is followed by cytokinesis.
Karyokinesis involves four stages: Prophase, Metaphase, Anaphase and Telophase.
Prophase:
It is the first stage of karyokinesis.
Condensation of chromosomes takes place.
Each chromosome has two chromatids
The cell organelles like endoplasmic reticulum, golgi complexes, nucleolus and nuclear envelope disappear.
Centrosome begins to move towards opposite poles of the cell. Each centrosome radiates out microtubules called asters. The two asters together with spindle fibres forms mitotic apparatus.
