7th Grade Science Cell Cycle

How do little elephants grow up to be BIG elephants?

Why do animals shed their skin?

Three reasons why cells reproduce exact copies of each other by mitosis are: 1. Growth 2. Repair 3. Replacement Cells that reproduce by mitosis reproduce constantly!

Animated Mitosis Cycle http://www.cellsalive.com/mitosis.htm Interphase Prophase Metaphase Anaphase Telophase & Cytokinesis

“Cell growth and development” Interphase “Cell growth and development”

Interphase (occurs before Mitosis begins) A cell grows in size, performs its function, and creates organelles needed to perform functions Chromatin are copied (# doubles) called sister chromatin A cell creates specific organelles for the purpose of dividing (Centrioles, Spindle Fibers) A cell spends most of its life in this phase! CELL MEMBRANE Nucleus Cytoplasm

Interphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

“Division of the nucleus” Mitosis “Division of the nucleus”

Prophase 1st step in Mitosis Chromitin condenses to form chromatids and begin to attach to sister chromatids (clones from interphase) Centrioles appear and begin to move to opposite ends of the cell and spindle fibers form between the centrioles. Nuclear Envelope begins to break down. Centrioles Sister chromatids Spindle fibers

Prophase Plant Cell Animal Cell Spindle fibers Centrioles Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Metaphase 2nd step in Mitosis Chromatids attach and move to the equator (middle) of the cell Sister Chromatids (or pairs of chromosomes) attach to the spindle fibers at the centromere Centromere Centrioles Spindle fibers

Metaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Anaphase 3rd step in Mitosis Centromeres split and sister chromatids (or pairs of chromosomes) separate Sister chromatids begin to move to opposite ends of the cell Opposite ends of the cell begin to push apart Centrioles Spindle fibers

Anaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Telophase 4th step in Mitosis Nuclear envelope begins to form and two new nuclei form. Chromosomes appear as chromatin (threads rather than rods). (Mitosis ends) Nuclei Nuclei Chromatin

Telophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

“Division of the cytoplasm” Cytokinesis “Division of the cytoplasm”

Cytokinesis occurs after mitosis Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes.

Animal Mitosis -- Review Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

Plant Mitosis -- Review Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

Mitosis Animation http://www.cellsalive.com/mitosis.htm