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G1 Phase  The first stage of interphase is called the  G1 phase



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English for Biology A Teacher Resource Manual

G1 Phase 
The first stage of interphase is called the 
G1 phase
, or first gap, because little change is visible. 
However, the cell is quite active at the biochemical level during the G1 stage. The chromosomal DNA and 
protein building blocks are being accumulated by the cell, and it is also storing enough energy to finish 
replicating each chromosome in the nucleus. 
S Phase 
Throughout the interphase, nuclear DNA remains in a semi-condensed chromatin configuration. In the 
S phase
(synthesis phase), Sister chromatids, which are tightly joined at the centromere region of each 
chromosome, are created as a result of DNA replication and are two identical copies of each chromosome. At 
this stage, each chromosome is made of two sister chromatids and is a 
duplicated chromosome
. The 
centrosome is duplicated during the S phase. The 
mitotic spindle
, which directs the movement of chromosomes 
during mitosis, will develop from the two centrosomes. The centrosome consists of a pair of rod-like 
centrioles
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https://www.youtube.com/watch?v=Wy3N5NCZBHQ
  


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at right angles to each other. Cell division is organized by centroles. Many eukaryotic species, including most 
fungi and plant species, lack centrioles in their centrosomes. 
G2 Phase 
In the 
G2 phase
, or second gap, The cell produces the proteins required for chromosome manipulation 
as well as replenishes its energy reserves. To give the mitotic spindle resources, some cell organelles are 
duplicated, and the cytoskeleton is disassembled. During G2, additional cell growth might occur. Before the 
cell can enter the first stage of mitosis, the last preparations for the mitotic phase must be finished
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