Question

which of the following is an example of an external checkpoint of the cell cycle? *
p. g1 checkpoint
q. g2 checkpoint
r. m checkpoint
s. hormones
which checkpoint tries to make sure that the correct amount of dna (number of chromosomes) is being divided into each cell?
a. g1 checkpoint
b. g2 checkpoint
c. m checkpoint
d. t checkpoint

Explanation:

• First question:
• G1, G2, and M checkpoints are internal checkpoints. They monitor the cell's internal state (e.g., DNA damage, cell size). Hormones are external signals that can influence the cell cycle. For example, growth - promoting hormones can signal a cell to enter the cell cycle.
• Second question:
• The M checkpoint (also known as the spindle - assembly checkpoint) ensures that chromosomes are properly attached to the spindle fibers before anaphase. This is crucial for the correct division of chromosomes (and thus the correct amount of DNA) into daughter cells. The G1 checkpoint checks for cell size, nutrients, and DNA damage. The G2 checkpoint checks for DNA replication completeness. There is no T checkpoint in the standard cell - cycle checkpoints.

Answer:

• First question: S. Hormones
• Second question: C. M checkpoint