Cell Growth & Division Mitosis
Why do Cells Reproduce? Growth of an organism Replacement of old or damaged cells
Chromosomes Each cell has lots of DNA, but it must be condensed in order to fit in the nucleus DNA is organized and packaged into structures called chromosomes Prokaryotic Chromosome: –Single circular strand of DNA that is condensed through many twists Eukaryotic Chromosome…
Eukaryotic Chromosomes Most eukaryotes have between 10 & 50 chromosomes in their body cells, but… Chromosomes can’t be seen when cells aren’t dividing and are called chromatin
Eukaryotic Chromosomes When cells are ready to divide, the chromatin condenses into chromosomes Each of the 2 thick strands is called a chromatid Identical chromatids (sister chromatids) are held together at centromere
Preparing for Cell Division All newly-formed cells require DNA, so before a cell divides, a copy of DNA is made for each new cell (daughter cell) This assures that new cells will work in the same way as the cells they came from
In prokaryotic cells, it’s simple!! DNA is copied, then cell divides In eukaryotic cells, it’s more complex… Preparing for Cell Division
Eukaryotic Cell Cycle: Overview 1.) Interphase: when cell grows and prepares to divide 2.) Mitosis: when nucleus divides 3.) Cytokinesis: when cytoplasm divides and two new cells are complete
Interphase Growth stage Cells mature by making more cytoplasm Organelles and Centrioles duplicate DNA is copied Two identical copies of DNA Original DNA
Prophase Metaphase Anaphase Telophase PMAT!! Mitosis
Prophase Chromatin in nucleus condenses to form visible chromosomes Spindle fibers form from the centrioles and attach to centromeres
Metaphase Chromosomes that are attached to spindle fibers move to the center of the cell and line up
Anaphase Occurs Rapidly Sister chromatids are pulled apart to opposite poles of cell by spindle fibers
Telophase Sister chromatids are at opposite poles Spindles disassemble Nuclear envelope forms around each set of sister chromatids
Cytokinesis Division of cytoplasm Division of cell into two, identical cells called daughter cells Daughter cells have the same # of chromosomes as each other and as the parent cell from which they were formed Must still grow in size to become mature
Onion Root Tip Interphase Prophase Metaphase Anaphase Telophase Cytokinesis
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