Multicellular organisms use cell division, mitosis, for growth and the maintenance and repair of cells and tissues. There are few cells in the body that 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. Explain the purpose of the areas labelled checkpoint in the cycle? All BUT ONE could apply.
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.