Cell Cycle Cell Cycle

The repeating set of The repeating set of events in the life of a events in the life of a cell.cell.

Includes Includes InterphaseInterphase

3 phases3 phases

Cell DivisionCell Division MitosisMitosis Cytokinesis Cytokinesis

InterphaseInterphase

Period between cell divisions, 3 stages-Period between cell divisions, 3 stages- 1. G1. G11 phase- phase- Gap 1-Gap 1- Cells grow to mature size. Cells grow to mature size. 2. S phase- 2. S phase- SynthesisSynthesis- DNA replication.- DNA replication. 3. G3. G22 phase- phase- Gap 2-Gap 2- Cell prepares for cell division. Cell prepares for cell division.

GGOO phase- Cell exits the cell cycle (usually after phase- Cell exits the cell cycle (usually after

GG11) Cells do not copy DNA or prepare to divide. ) Cells do not copy DNA or prepare to divide.

Ex. CNS cells stop dividing at maturity and never Ex. CNS cells stop dividing at maturity and never divide again.divide again.

MitosisMitosis

Division of the nucleus.Division of the nucleus. Distributes the cells copied DNA to offspring Distributes the cells copied DNA to offspring

cells.cells. New cells get the same number and kinds of New cells get the same number and kinds of

chromosomes as the parent cellchromosomes as the parent cell 4 phases 4 phases

Prophase (p 156)Prophase (p 156)

Chromosomes shorten, thicken and become Chromosomes shorten, thicken and become visiblevisible

Chromatids (replicated chromosomes) lie Chromatids (replicated chromosomes) lie side by side, attached by a centromereside by side, attached by a centromere

Centrioles move to opposite ends of the cell Centrioles move to opposite ends of the cell (animal cells)(animal cells)

Nuclear membrane breaks downNuclear membrane breaks down

Metaphase (pp 156, 157)Metaphase (pp 156, 157)

Paired chromosomes line up at the equator of Paired chromosomes line up at the equator of the cellthe cell

Centromeres attach to the spindleCentromeres attach to the spindle

Anaphase (156, 157)Anaphase (156, 157)

Centromeres splitCentromeres split Chromatids separate, becoming individual Chromatids separate, becoming individual

chromosomeschromosomes Chromosomes move to opposite poles along Chromosomes move to opposite poles along

spindlespindle

Telophase (p 156, 157)Telophase (p 156, 157)

Chromosomes uncoil into tangle of Chromosomes uncoil into tangle of chromatinchromatin

Nuclear envelope reforms around the Nuclear envelope reforms around the chromatinchromatin

Cytokinesis (p 157)Cytokinesis (p 157)

The division of the cytoplasm into two cellsThe division of the cytoplasm into two cells Animal cells- cell membrane pinches the Animal cells- cell membrane pinches the

cytoplasm into two equal partscytoplasm into two equal parts Plant cells- cell plate forms midway between Plant cells- cell plate forms midway between

divided nuclei, plate becomes cell walldivided nuclei, plate becomes cell wall