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Cell Division.

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Presentation on theme: "Cell Division."— Presentation transcript:

1 Cell Division

2 Cell division – parent cell divides into 2
daughter cells 2 types of cell division: 1) mitosis – division of somatic (body) cell to produce identical somatic cells -occurs in a series of phases

3 Interphase part of cell cycle when cell is not dividing
DNA replication occurs during this time as well as all other cell activities *includes G1, S, and G2

4 Prophase first phase of mitosis
chromatid pairs shorten, thicken, become visible centrioles move to opposite poles spindle fibers form (between centrioles) nuclear membrane, nucleolus disappear *Plant cells have no centrioles, but spindle still forms

5 Metaphase chromatid pairs line up along middle of spindle (equator)
spindle fibers attach to centromere of each chromatid pair

6 Anaphase chromatid pairs move to opposite poles of the spindle
separation of chromatid pairs signals the start of anaphase

7 Telophase final phase of mitosis
begins when chromosomes arrive at poles chromosomes get longer, thinner spindle breaks down nuclear membrane forms around each set of chromosomes, nucleolus reappears cell begins to divide in two

8 Telophase cytokinesis – division of cytoplasm
Plant cell vs. Animal cell cytokinesis: Plant – Animal - cell plate forms, membrane pinches elongates, forming inward & forms a new cell wall depression or cell furrow

9 2) Meiosis – division of germ cells (diploid somatic cells) to produce monoploid/haploid cells (gametes) Diploid – (2n) – two copies of each chromosome Haploid/monoploid – (1n) – one copy of each chromosome

10 Meiosis Interphase – DNA replication
Prophase I – homologous chromosomes pair up & form 4-stranded groups called tetrads -chromosomes enlarge, exchange corresponding segments of DNA (crossing over)

11 Meiosis chromosomes shorten, thicken, become visible
spindle forms, nuclear membrane & nucleolus break down Metaphase I – tetrads move toward middle of spindle & line up along equator -spindle fibers attach to centromeres

12 Meiosis Anaphase I – chromatid pairs forming each tetrad move to opposite poles Telophase I – nuclear membrane reappears -cytoplasm begins to divide & form either cell plate or cell furrow (This first division is the reduction division) Meiotic Interphase – NO DNA replication

13 Meiosis Prophase II - chromatid pairs shorten/thicken -no tetrads (since they already separated in the first division) -spindle begins to form; nuclear membrane breaks down

14 Meiosis Metaphase II – paired chromatids line up at the equator; spindle fibers attach to centromeres of each chromatid Anaphase II – members of each chromatid pair move apart to opposite poles Telophase II – nuclear membrane reappears; cytokinesis occurs; chromosomes become long, thin

15 Meiosis 4 haploid cells result (gametogenesis)
Spermatogenesis – formation of sperm -4 evenly sized cells Oogenesis – formation of egg cells -1 egg & 3 small polar bodies

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