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  • Correct sequence of phases in cell cycle is  Option: 1 M → G1→G2 → S  <s

Correct sequence of phases in cell cycle is
 

Option: 1

M → G1→G2 → S
 


Option: 2

G1 → G2 → S → M
 


Option: 3

S→ G1 → G2 → M
 


Option: 4

G1 → S → G2 → M
 


Answers (1)

 

 

Cell Cycle: Interphase -

Cell Cycle: Interphase

  • Cell spent most of its 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 most active phase of cell cycle. 
  • The interphase last more than 95% of the duration of the cell cycle.
  • It was earlier regarded as 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:
1. G1 - phase or Pre DNA synthesis phase (First Gap phase):

  • The cell recovers from the previous division.
  • The cell increases in size, doubles its organelles (such as mitochondria and ribosomes), and accumulates materials that will be used for DNA synthesis.
  • Cells are constantly performing their normal daily functions, including communicating with other cells, secreting substances, and carrying out cellular respiration.

2. S - phase (DNA synthesis phase):

  • Following G1, the cell enters the S stage, when DNA synthesis or replication occurs.
  • At the beginning of the S stage, each chromosome is composed of one DNA double helix.
  • Following DNA replication, each chromosome is composed of two identical DNA double helix molecules.
  • Each double helix is called a chromatid.
  • Another way of expressing these events is to say that DNA replication has resulted in duplicated chromosomes, and the two chromatids will remain attached until they are separated during mitosis.
  • If the initial amount of DNA is denoted as 2C then it increases to 4C.
  • However, there is no increase in the chromosome number; if the cell had diploid or 2n number of chromosomes at G1, even after S phase the number of chromosomes remains the same, i.e., 2n.

 

3. G2 - phase (Second Gap phase) or Post DNA synthesis phase:

  • Following the S stage, G 2 is the stage from the completion of DNA replication to the onset of mitosis.
  • At this stage, the proteins that will be helpful during the cell division are synthesized.
  • For example, proteins that form microtubules will be synthesized.

-

 

 

The correct sequence of cell cycle is G1 → S → G2 → M

Posted by

Sumit Saini

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