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The Cell Cycle

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  1. The Cell Cycle Section 10-2 Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming Go to Section:

  2. Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming Go to Section:

  3. Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming Go to Section:

  4. Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming Go to Section:

  5. Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming Go to Section:

  6. Figure 10–5 Mitosis and Cytokinesis Section 10-2 Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming Go to Section:

  7. Meiosis *Gametes are special cells used in sexual reproduction. It is important that these cells contain 1/2 the normal number of chromosomes than the regular body cells. *When the sperm and egg unite the resulting zygote will contain the normal number of chromosomes for that organism

  8. Mitosis- formation of body cells. At the end of mitosis each of the 2 daughter cells has 46 chromosomes • These are your body cells, cells that make up tissues, organs, etc • Meiosis-formation of sex cells called gametes. At the end of meiosis each of the 4 daughter cells has 23 chromosomes. • They contain half the number of chromosomes

  9. Cell division cell type # of daughter # of cells chromosomes Mitosis somatic(body) 2 46(diploid) Meiosis gametes(sex) 4 23(haploid) Meiosis reduces the number of chromosomes to half the number in body cells. This is called the haploid number. Reductive division is necessary so that when reproduction occurs, the zygote contains the necessary 46. Egg(23 chrom) + sperm(23 chrom) = zygote(46 chrom)

  10. Meiosis There are 2 divisions of meiosis- Meiosis I and Meiosis II. It must be this way in order to end up with the sex cells only having 23 chromosomes.

  11. Meiosis I During the first meiotic division, chromosomes are replicated. 1. Prophase I- chromatin makes a copy of itself and begins to coil up

  12. 2. Metaphase I- homologous pairs of chromosomes line up together at the middle of the cell. This forms a tetrad(meaning 4). Homologous chromosomes are paired chromosomes. Each contains genes for the same trait.

  13. 3. Anaphase I- homologous chromosomes that form each tetrad separate and move to opposite ends. The centromeres do not split.

  14. 4. Telophase I- spindle disappears and the cell divides.

  15. Meiosis II During the second meiotic division, nothing is replicated. 1. Prophase II- centriole doubles, spindle forms

  16. 2. Metaphase II- chromosomes line up at the middle

  17. 3. Anaphase II- individual chromatids move to opposite ends

  18. 4. Telophase II- when the 2 daughter cells divide into 4 new daughter cells, each new daughter cell has 23 chromosomes. This is half the number of the original parent cell.

  19. Meiosis • Meiosis occurs in the testes of the male and is called spermatogenesis. 4 sperm are produced. • And in the ovaries of the female it is called oogenesis. 4 cells are produced but only 1 becomes an egg, the other 3 dissolve.

  20. What type of cell is made during meiosis? • Somatic b. gametic 2. Gametes contain ______ chromosomes. a. 25 b. 46 c. 23 d. 50 3. There are ___ divisions of meiosis. a. 3 b. 4 c. 2 d. 5 4. Meiosis in males leads to the production of 4 _____ cells. a. egg b. sperm c. ovum 5. At the end of _____(what phase) in meiosis I, 2 daughter cells are formed. a. interphase b. metaphase c. telophase d. anaphase