Question

multicellular organisms use cell division and mitosis to grow, maintain, and repair cells and tissues. few cells in the body do not undergo mitosis: most somatic cells divide regularly, some more than others. single - celled organisms may use cell division as their method of reproduction. regardless of the reason for mitosis, the process ensures genetic continuity. consider the model of the cell cycle.
which statement does not correctly explain the purpose of the areas labeled checkpoint in the cycle?
a g1 the checkpoint where an animal cell becomes committed to the cell cycle, which is determined by external factors and signals.
b the spindle checkpoint prevents separation of the duplicated chromosomes until each chromosome is properly attached to the spindle fibers.
c the g2 checkpoint ensures all of the chromosomes have been replicated and that the replicated dna is not damaged before cell enters mitosis.
d cell size, protein reserves, and damage to dna is evaluated at the s checkpoint; the cell will not be allowed to continue if any problems are detected.

Explanation:

To determine the incorrect statement about cell cycle checkpoints:

• Option A: The G1 checkpoint (restriction point) is where a cell commits to the cell cycle, influenced by external signals. This is correct.
• Option B: The spindle checkpoint (in mitosis) ensures chromosomes are properly attached to spindle fibers before separation. This is correct.
• Option C: The G2 checkpoint verifies DNA replication and checks for damage before mitosis. This is correct.
• Option D: The S phase is for DNA synthesis, not a checkpoint for cell size, protein reserves, or DNA damage. Those checks occur at the G1 checkpoint (before S phase) and G2 checkpoint (after S phase). So this statement is incorrect.

Answer:

D. Cell size, protein reserves, and damage to DNA is evaluated at the S checkpoint; the cell will not be allowed to continue if any problems are detected.