Question

9) The stage of the cell cycle where errors made during DNA replication get corrected:

a) S

b) G2

c) G1

d) M

e) G0

Answer 1

The stage of the cell cycle where errors madeduring DNA replication get corrected : b)G2

Cell cycle is divided into four different phases:

1) G1 phase- RNA and proteins are synthesized and cell is preparing for DNA replication.

2) S phase- DNA is replicated.

3) G2 phase- cell has two diploid sets of chromosomes. Cell is preparing for division.

4) M phase- The period of actual division.

Cell cycle is regulated by mainly 3 checkpoints: G1 checkpoint, G2 checkpoint, Spindle assembly checkpoint.

I) G1 checkpoint ensures whether a cell is going to divide or not. Once a cell passes this period, it enters S phase.

II) Once DNA replication is completed, cell is halted at another checkpoint, G2 checkpoint which checks for DNA damage, DNA replication errors. If any kind of replication error occurs, cell pauses at G2 checkpoint and repair is being done. If repair is not done, then cell is going to be killed by the process of apoptosis.

III) At the end of G2 phase or prior to the M phase Spindle assembly checkpoint ensures all chromosome kinetochores are attached to spindle microtubules before anaphase.