<P> During G phase, the cell grows in size and synthesizes mRNA and proteins (Known as histones) that are required for DNA synthesis . Once the required proteins and growth are complete, the cell enters the next phase of the cell cycle, S phase . The duration of each phase, including the G phase, is different in many different types of cells . In human somatic cells, the cell cycle lasts about 18 hours, and the G phase takes up about 1 / 3 of that time . However, in Xenopus embryos, sea urchin embryos, and Drosophila embryos, the G phase is barely existent and is defined as the gap, if one exists, between the end of mitosis and the S phase . </P> <P> G phase and the other subphases of the cell cycle may be affected by limiting growth factors such as nutrient supply, temperature, and room for growth . Sufficient nucleotides and amino acids must be present in order to synthesize mRNA and proteins . Physiological temperatures are optimal for cell growth . In humans, the normal physiological temperature is around 37 ° C (98.6 ° F). </P> <P> G phase is particularly important in the cell cycle because it determines whether a cell commits to division or to leaving the cell cycle . If a cell is signaled to remain undivided, instead of moving onto the S phase, it will leave the G phase and move into a state of dormancy called the G phase . Most nonproliferating vertebrate cells will enter the G phase . </P> <P> Within the cell cycle, there is a stringent set of regulations known as the cell cycle control system that controls the timing and coordination of the phases to ensure a correct order of events . Biochemical triggers known as cyclin - dependent kinases (Cdks) switch on cell cycles events at the corrected time and in the correct order to prevent any mistakes . </P>

If a eukaryotic cell is in the g1 phase of the cell cycle