\nThe cell cycle is a top-down view of how a cell spends its time. It’s divided into two main phases, interphase (preparing to divide) and mitosis (cell division). Interphase is subdivided into G1, S, and G2; about 90% of the time, a cell will be in interphase.<\/p>\n
\nG1 is an accumulation and growth phase: the cell is building up energy resources, as well as its stock of proteins and DNA components, to prepare for replication of its chromosomes.<\/p>\n
\nDuring the S phase, the chromosomes are replicated; each copy is stuck to its original by a centromere. One might refer to the two identical chromosomes in such a pair as sister chromatids. Some people refer to them as a single chromosome, perhaps because they contain information from only one; they’re just two copies of it. Also during the S phase, the centrosome is copied. This is also preparation towards mitosis.<\/p>\n
\nNext, in the G2 phase, the cell restores the energy reserves drawn down during the S phase. As well, more proteins are synthesized that will be used during mitosis. Some of the cell’s specific structures (organelles) are copied. Moreover, the cytoskeleton, a network of fibres used to cause movement within the cell, is taken apart; its parts will be repurposed as the spindle, which carries out separation of sister chromatids into two sets during mitosis.<\/p>\n
\nFinally, mitosis occurs: the cell divides into two identical sister cells. After mitosis, the cell re-enters G1.<\/p>\n
Source:<\/p>\n
bio.libretexts.org<\/a><\/p>\n bio.libretexts.org<\/a><\/p>\nJack of Oracle Tutoring by Jack and Diane,<\/a> Campbell River, BC.\n","protected":false},"excerpt":{"rendered":" Tutoring biology (aka life science), one encounters the cell cycle. The tutor summarizes it. The cell cycle is a top-down view of how a cell spends its time. It’s divided into two main phases, interphase (preparing to divide) and mitosis …<\/p>\n