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Why do cells divide? Growth and Repair Creation of gametes 2

Chromosomes 3 Made of densely packed DNA Human Eukaryotic Cells 1.Somatic (body) cells A.46 chromosomes b.Diploid 2.Sex cells (gametes) a.23 chromosomes b.Haploid Why would sex cells need half the number of chromosomes ?

Karyotype 4 Homologous Chromosomes --Chromosome pairs that carry genes for the SAME trait An organized profile of persons chromosomes

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6 Phases of The Cell Cycle 3 G1,S, and G2 are known together as Interphase.

7 Somatic cell cycle G1 phase- Gap phase, cell undergoes growth. S phase- DNA synthesis (replication) G2 phase- Gap phase. Preparation for Mitosis. Organelles are produced. Interphase Body Cells Sex cells are called gametes 4

8 Mitosis Nuclear Division. Nucleus divides once into two identical nuclei with the same DNA YEILD: 2 diploid somatic cells 11

9 Meiosis Nuclear Division. Nucleus divides twice into four =nuclei with different DNA YEILD: 4 haploid gametes 11

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MitosisMeiosis 1.Which type of cells go through Mitosis? 5.Which type of cells go through Meiosis? 2.The nucleus divides into how many nuclei? 6.How many times does the nucleus divide? 3.Is the DNA the same or different? 7.Is the DNA the same or different? 4.What does mitosis yield ( or make) ? 8.What does meiosis yield ( or make)? 11

MitosisMeiosis 1.Which type of cells go through Mitosis? Somatic ( Body) 5.Which type of cells go through Meiosis? Gametes (Sex) 2.The nucleus divides into how many nuclei? 2 6.How many times does the nucleus divide? 2 3.Is the DNA the same or different? same 7.Is the DNA the same or different? different 4.What does mitosis yield ( or make) ? 2 identical diploid somatic cells 8.What does meiosis yield ( or make)? 4 different haploid gametes 12

13 4 Steps of Mitosis (PMAT) Prophase: Chromosomes condense Nuclear membrane breaks down. Centrioles move to opposite sides of the cells 12

14 Metaphase: Metaphase: -Chromosomes attach to spindle fibers -Chromosomes line up in the middle of the cell

15 Anaphase: -Chromosomes separate -Chromosomes move to opposite sides of the cell 15

16 Telophase There are now TWO nuclei in one cell! 16 …And they contain the SAME genetic information *SAME NUMBER OF CHROMOSOMES Nuclear Envelope reforms

17Cytokinesis Cytoplasmic divisionCytoplasmic division Each cell gets half of the organelles.Each cell gets half of the organelles. cell pinches in half to form two new cells.cell pinches in half to form two new cells. 19

18 In plant cells a cell plate forms from the inside out. 21

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21 Mitosis in Onion 25

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24 29 includes is divided into Concept Map Cell Cycle M phase (Mitosis) Interphase G 1 phase S phase ProphaseG 2 phaseMetaphaseTelophaseAnaphase

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26Cytokinesis Animal cells pinch.Animal cells pinch. Cytokinesis in plant cells is different from that in animal cells.Cytokinesis in plant cells is different from that in animal cells. 20

27 Cell Size Why not just one large cell? Difficult to get nutrients in and waste out 2

28 G 1 Phase Cell growsCell grows 5

29 S Phase Chromosomes Condense Chromosomes are inherited genetic information Chromosomes are made up of DNA Can only be seen when cells are dividing 6

30 S Phase Chromosomes replicate-or copy is madeChromosomes replicate-or copy is made The two copies areThe two copies are -attached together at a point called a centromere. -attached together at a point called a centromere. -are called sister chromatid. -are called sister chromatid. 7

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32 G2 Phase Organelles must be replicated (copied) 9 9

33 M Phase Two parts: 1.Nuclear division –Mitosis 2.Cytoplasmic Division –Cytokinesis 10

34 Mitosis review video clip with quiz! Mitosis review video clip with quiz! 22

35 Results of Mitosis and Cytokinesis Two new cells. called daughter cells-The new cells- called daughter cells- have the same number of chromosomes as the mother cell. This occurs in all somatic cells in your body. You have 46 chromosomes in all of your somatic cells-23 pair! 24

36 Cells during Mitosis 26

37 Reproduction of Sex Cells Sex cells- Sperm and egg Process is called Meiosis Similar to Mitosis 30

38 Meiosis Cell divides twiceCell divides twice First division is like mitosis and then the cell divides again to create 4 haploid cells.First division is like mitosis and then the cell divides again to create 4 haploid cells. 31

39 MEIOSIS=CHROMOSOME REDUCTION DIVISION 32

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41Meiosis Meiosis is also know as chromosome reduction division. Start with 46 and ends up with 23. Why? Fertilization creates the diploid condition again Diploid Haploid 34

42 Sperm formationSperm formation- 4 haploid sperm cells are formed. Egg formationEgg formation-most of the cytoplasm is used in one cell and the other three disintegrate. One haploid egg cell is formed. 35

43 Meiosis Video Clip 36

44 Crossing Over Sometime during meiosis the chromosomes can exchange information This is called Crossing Over Major source of genetic diversity in the species 37

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46 Prokaryotic Cells Binary fission Occurs in Prokaryotic Cells DNA is copied and then the cell splits in half. 39

47 Regulation of the Cell Cycle How do cells know when to divide? When to stop dividing? Cyclins-proteins that regulate the cell cycle. 40

48 Cancer Unregulated cell growth. Can form masses of cells called tumors. 41