How do little elephants grow up to be
How do little elephants grow up to be BIG elephants? How does a little elephant come to be?
CELL DIVISION!!
There are two types of cell division. Mitosis – when an organism is growing, repairing or replacing cells EX: skin cells replacing dead skin cells Meiosis – when it’s time to reproduce an organism EX: when you were created!
Meiosis or Mitosis? A) A snake sheds its skin. B) My dog just had puppies. C) You grew four inches in the last 2 years.
MITOSIS
Mitosis Cycle http: //www. youtube. com/watch? v=NR 0 md. DJMHIQ&feature=related • Interphase • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis
Interphase • The cell prepares to divide by copying its DNA
Interphase Animal Cell Plant Cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm
Prophase • The chromatin in the nucleus condenses and forms chromosomes. • Centrioles appear at the poles of the cell. • The nuclear envelope breaks down.
Prophase Animal Cell Plant Cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm
Metaphase The centrioles attach spindle fibers to the centers of each chromatid (a pair of chromosomes) • The chromatids are being pulled in both directions, so they end up lined up across the center of the cell. •
Metaphase Animal Cell Plant Cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm
Anaphase 3 rd step in Mitosis The chromatids split up; half moving toward one pole and the other half moving toward the other pole. • The cell begins to stretch. •
Anaphase Animal Cell Plant Cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm
Telophase • Two new nuclear envelopes form. • The chromatids loosen up and appear as chromatin again
Cytokinesis • The cell membrane pinches into two ‘daughter cells’ that are exactly the same as the ‘parent cell. ’
Animal Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase
Plant Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase
Cell Cycle 20
MEIOSIS
Meiosis Interphase Meiosis is preceded by interphase. The chromosomes have not yet condensed. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html
Meiosis Interphase The chromosomes have replicated, and the chromatin begins to condense. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html
Meiosis Prophase I The chromosomes are completely condensed. In meiosis (unlike mitosis), the homologous (same) chromosomes pair with one another http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html
Meiosis Metaphase I The nuclear membrane dissolves and the chromosomes attach to the spindle fibers. They are preparing to go to opposite poles. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html
Meiosis Anaphase I The chromosomes move to opposite ends of the cell. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html
Meiosis Telophase I & Cytokinesis The cell begins to divide into two daughter cells. It is important to understand that each daughter cell can get any combination of maternal and paternal chromosomes. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html
Meiosis Prophase II The cell has divided into two daughter cells. These cells are diploid, they have a full set of chromosomes. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html
Meiosis Metaphase II As in Meiosis I, the chromosomes line up on the spindle fibers. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html
Meiosis Anaphase II The two cells each begin to divide. As in Meiosis I, the chromosomes move to opposite ends of each cell. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html
Telophase II & Cytokinesis With the formation of four cells, meiosis is over. Each of these daughter cells have half the chromosomes of parent cells, which is called, haploid. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html
• Meiosis is basically the same as mitosis, BUT it happens twice and it ends up with four cells at the end. • AND the four ‘daughter cells’ only have half of the chromosomes that the ‘parent cell’ had.
Mitosis Vs. Meiosis Mitosis - Divides body cells Meiosis - Divides sex cells - Same number of chromosomes as original cell (diploid) - End up with ½ of the chromosomes of original cell (haploid) - The 2 daughter cells at the end will have 46 chromosomes (23 pair) - The 4 daughter cells at the end will each have 23 chromosomes
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