What is meant by the term “cycle” in cell cycle?  What is happening in the S phase and M phase?

A cell can normally halt its progression through the cell cycle at different checkpoints. Which of the following best predicts a reason for a cell to halt its progression through the cell cycle between the G1 and the S phases? A B incorrect attachment of spindle fibers to sister chromatids с insufficient accumulation of nucleotides D mitosis-facilitating enzymes have not been synthesized errors in DNA replication during G1

2.) One experimental tool used in the biological research and in clinical settings is called Fluorescent Activated Cell Sorting (FACS) or cell cytometry. For example, a cell membrane permeable (or nonpolar) chemical called Hoescht 33342 dye will specifically label DNA. Interpret the graph (Figure 17-4) that illustrates normal cells that have been labeled with Hoescht 33342 dye, and assign which phase(s) of the cell cycle (G1, S, G2, or M) corresponds to the fluorescence intensity. Justify your answers. 1 relative fluorescence per cell Figure 17-4 Analysis of Hoechst 33342 fluorescence in a population of cells sorted in a flow cytometer (Problem 17-15). number of cells