Cell Reproduction—Mitosis Section 8.2

Look at the five cells outlined below Look at the five cells outlined below. Put them in order to show as best you can to show the process of cell division. C A D E B

Make a foldable with ____ flaps. 2 Flaps on Left: 1--Why do cells divide? 2—Cell Cycle 4 flaps on Right: Prophase Metaphase Anaphase Telophase

Why do cells reproduce at all? Couldn’t they grow really, really big? Cells need to divide in order to… Replace dead cells. Grow their population (unicellular organisms) Continue functioning properly (they can’t work if they get too big)

Review: all cells come from preexisting cells This means that when a cell reproduces or divides, it creates two cells that are identical to the original. This occurs not only because it is better to have many small cells, but also because an organism needs to grow or replace dead tissue. (This also will cause population growth in unicellular organisms.)

Chromosomes carry the coiled DNA.

The Cell Cycle The cell cycle is the steps a cell goes through during its life. Interphase: Cell growth & DNA replication. The cell spends most of its time in this stage. Mitosis: Process where the cell divides to make two new cells, each with a full set of chromosomes. Cytokinesis: The conclusion of cell division, when the two new cells actually separate.

Steps of Mitosis Prophase – “pro” means “before” Metaphase – “meta” means “middle” Anaphase – “ana” means “apart” Telophase – “telo” means “end” **Use the terms to provide clues for what happens in each step** Pro - prepares Ana - apart Meta - middle Telo - two

Prophase Chromatin (DNA) coils into chromosomes. The nuclear membrane is disappearing. In animal cells, centrioles and spindle fiber have formed and are lining up in the cell.

Metaphase Chromosomes become attached to the spindle fibers at the centromere. Spindle fibers help to position chromosomes in the middle of the cell, so each sister chromatid is facing a pole.

Anaphase Sister chromatids are pulled apart towards opposite poles.

Telophase Chromatids begin to uncoil. Two new nuclei are formed. Cytokinesis: A new cell membrane begins to form down the middle of cell.