10-2 Cell Division

Why do Cells divide? Overload its DNA Exchange of materials

The Cell Cycle A series of events that a cell goes through as they grow and divide Cell grows Prepared to divide This time in between divisions is called “Interphase” Divides – forming two daughter cells Each daughter cell repeats the cell cycle

Chromosomes DNA is carried from one generation of cells to the next generation by chromosomes Chromosomes are made up of DNA and proteins

Before Cell Division Each chromosome is replicated (copied), this results in two identical “sister” Chromatids.

Mitosis tug-of-war 4 phases Prophase, metaphase, anaphase, telophase

Prophase Chromosomes become Visible Longest phase The centrioles, separate and take positions on opposite sides of the nucleus Centrioles acts as the anchors in the tug-of-war Spindles begin to form, and attach to the chromosomes Spindles are the ropes for the tug-of-war Nuclear envelope (membrane) breaks down

Metaphase Chromosomes line up across the center of the cell Shortest phase Chromosomes line up across the center of the cell tug-of-war is set and ready

Anaphase The centromeres begin to separate The tug-of-war begins The centromeres begin to separate the Chromatids split, and become single chromosomes The chromosomes continue to move until they are at opposite sides of the cell

Telophase The chromosomes begin to disperse and disappear The nuclear envelope (membrane) reforms around each cluster of chromosomes Spindles break apart and disappear Tug-of-war is over = it’s a tie

Mitosis is over, but cell division is not There is now one cell with two nuclei (nucleuses), each with a duplicate set of chromosomes Cell must go through Cytokinesis

Cytokinesis The division of the cytoplasm Usually occurs at the same time as telophase In animal cells the cytoplasm pinches off In plant cells a cell plate forms which eventually becomes a membrane.

The End Result Started with one cell Ended with two cells, exactly the same as each other and exactly the same as the original cell.

End up with 2 identical cells Starts with 1 cell 2n End up with 2 identical cells 2n 2n