University of Central Florida (UCF) BSC2010C Biology I Practice Exam 3

The G0 phase is a state of dormancy in the cell cycle where cells are not actively dividing. This phase can occur when cells exit the cycle after completing mitosis but can re-enter the cell cycle in response to various signals if necessary. Nerve cells, or neurons, are predominantly found in the G0 phase because they generally do not divide after their initial development. Once formed, mature neurons are highly specialized for their functions in transmitting signals but do not proliferate, thereby maintaining their existence primarily within the G0 phase.

Muscle cells can also have differentiated forms that are not actively proliferating but can regenerate or fuse under certain conditions. Skin cells, particularly keratinocytes, are very active in their regenerative processes and frequently divide. Stem cells are typically in the cell cycle, poised to divide and differentiate into various cell types, rather than residing in a quiescent state like those in G0. Thus, the characteristic of nerve cells being specialized and largely non-dividing aligns them with the criteria for residing in the G0 phase.