The Cell Cycle Biology Fall 2016

Think About It….. When a living thing grows, what happens to its cells? What is there about growth that requires cells to divide and reproduce themselves?

Information “Overload” Living cells store critical information in DNA. As a cell grows, that information is used to build the molecules needed for cell growth. As size increases, the demands on that information grow as well. If a cell were to grow without limit, an “information crisis” would occur.

Information “Overload” Compare a cell to a growing town. The town library has a limited number of books. As the town grows, these limited number of books are in greater demand, which limits access. A growing cell makes greater demands on its genetic “library.” If the cell gets too big, the DNA would not be able to serve the needs of the growing cell.

Traffic Problems As the town grows, more and more traffic clogs the main street. It becomes difficult to get information across town and goods in and out. A cell that continues to grow would experience “traffic” problems. If the cell got too large, it would be more difficult to get oxygen and nutrients in and waste out.

The Prokaryotic Cell Cycle Binary fission is a form of asexual reproduction Two genetically identical cells are produced For example, bacteria reproduce by binary fission.

The Cell Cycle At this moment, millions of cells in the body are dividing, which is part of the process in the cell cycle. Cell Cycle- the regular sequence of growth and division that cells undergo which is divided into three main stages: Interphase Mitosis Cytokinesis

Stage 1: Interphase This is the time period before cell division where: The cell grows Makes a copy of its DNA Prepares to divide into two cells

The Eukaryotic Cell Cycle The eukaryotic cell cycle consists of four phases: G1 S G2 M.

The Eukaryotic Cell Cycle Interphase is the time between cell divisions. It is a period of growth that consists of the G1, S, and G2 phases. The M phase is the period of cell division.

Stage 2: Mitosis The stage during which the cell’s nucleus divides into two new nuclei- one copy of the DNA is distributed into each of the two daughter cells. Mitosis is divided into four phases: Prophase Metaphase Anaphase Telophase

Stage 3: Cytokinesis This is the final stage The cytoplasm divides The organelles are distributed into each of the two new cells. Usually begins during Telophase of mitosis

Cytokinesis in Animal Cells The cell membrane is drawn in until the cytoplasm is pinched into two equal parts. Each part contains its own nucleus and organelles.

Cytokinesis in Plant Cells In plants, the cell membrane is not flexible enough to draw inward because of the rigid cell wall. Instead, a cell plate forms between the divided nuclei that develops into cell membranes. A cell wall then forms in between the two new membranes.