CELL STRUCTURES AND FUNCTION
CELL CYCLE
|
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
|
|
|
G1 checkpoint
|
|
|
G2 checkpoint
|
|
|
M checkpoint
|
|
|
None of the above
|
Detailed explanation-1: -Damage to DNA and other external factors are evaluated at the G1 checkpoint; if conditions are inadequate, the cell will not be allowed to continue to the S phase of interphase. The G2 checkpoint ensures all of the chromosomes have been replicated and that the replicated DNA is not damaged before cell enters mitosis.
Detailed explanation-2: -This unleashes cyclin E-CDK2 and cyclin A-CDK2 activity, allowing further RB phosphorylation, exit from G1 and entry into S phase. The G1/S checkpoint is activated upon detection of DNA damage.
Detailed explanation-3: -At the G1 checkpoint, cells decide whether or not to proceed with division based on factors such as: Cell size. Nutrients. Growth factors. DNA damage.
Detailed explanation-4: -In addition to adequate reserves and cell size, there is a check for genomic DNA damage at the G1 checkpoint. A cell that does not meet all the requirements will not be allowed to progress into the S phase.
Detailed explanation-5: -The G2-M DNA damage checkpoint is an important cell cycle checkpoint in eukaryotic organisms that ensures that cells don’t initiate mitosis until damaged or incompletely replicated DNA is sufficiently repaired.