Describe what happens during the phases of the cell cycle.

Most cells going about their metabolic business are in G1. Cells preparing to divide enter S, the time of DNA synthesis, when DNA replication occurs. During G2, cells make the proteins needed for division. During mitosis, duplicated chromosomes condense. The two chromatids of duplicated chromosomes are readily visible. The nuclear envelope disassociates and the mitotic spindle forms. Chromosomes align on the equator and chromatids separate forming two identical groups of unduplicated chromosomes. The nuclear envelope reforms and the cells divide. Chromosomes decondense.