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Cell Reproduction

Cell Reproduction. Chapters 9 & 11. Types of Reproduction. Mitosis Asexual – only 1 parent needed & the offspring are identical to the parent cell. Meiosis Sexual – cells from 2 parents fuse to form new individual. These cells must have ½ the DNA of the parent cells. Cell Cycle.

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Cell Reproduction

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  1. Cell Reproduction Chapters 9 & 11

  2. Types of Reproduction Mitosis • Asexual – only 1 parent needed & the offspring are identical to the parent cell. Meiosis • Sexual – cells from 2 parents fuse to form new individual. These cells must have ½ the DNA of the parent cells.

  3. Cell Cycle • G1 – growth phase, most of life span • S – DNA synthesis ( 2-4 hrs) • G2 – short growth period (4-8 hrs) • M – mitosis or meiosis begins • G0 – cells that do not divide

  4. Events of the Cell Cycle Cell Cycle

  5. Mitosis • Mitosis is division of the nucleus • Cytokinesis is division of the cytoplasm • Nuclear material is DNA • Chromatin – diffuse DNA, spread out • Chromosomes – coiled DNA, compact • Eukaryotes have pairs of chromosomes

  6. figure 09-07.jpg Figure 9.7 Figure 9.7

  7. Phases of Mitosis Interphase • Non-dividing stage. G1, S, G2 • Cell carries on normal functions. • DNA and centrioles are replicated in preparation for cell division.

  8. Prophase • Chromosomes coil and become compact. • Chromosomes appear double stranded. • Chromatids attached at the centromere. • Centrioles move to the poles. • Asters form around centrioles. • Spindle fibers extend across the cell. • Nuclear membrane and nucleolus disappear.

  9. figure 09-09.jpg Figure 9.9 Figure 9.9

  10. Metaphase • Double stranded chromosomes individually line up on the equator • Centromeres attach to a spindle fiber CENTROMERE CENTRIOLE CHROMATID

  11. Anaphase • Chromosomes split & separate and are pulled to opposite poles of the cell by the spindle fibers

  12. Telophase • Cytoplasm divides (cytokinesis) • New nuclear membranes form • Plant cells build a new cell wall. • Animal cells pinch in and separate.

  13. Terminology MitosisMeiosis Asexual Type Sexual Diploid Chromo.# Haploid 2n n Zygotes Cell types Gametes

  14. Meiosis There are 2 cell divisions in meiosis. Interphase I • Chromosomes & centrioles replicate

  15. Prophase I • Chromosomes coil and become double stranded. • Centrioles move to the poles. • Asters and spindles form. • Nucleolus and nuclear membrane disappear. • Homologous chromosomes synapse. • Crossing over occurs. This results in the creation of variations in the chromosomes

  16. Metaphase I • Chromosomes line up in pairs on the equator. • Crossing over continues.

  17. Anaphase I • Homologous chromosomes separate and move to opposite poles. • Each new cell will receive 1 copy of the original chromosome pairs.

  18. Telophase I • Cytokinesis occurs. • Each cell has half the number of chromosomes as the original parent cell. • Chromosomes are still double stranded.

  19. Interphase II • Chromosomes are uncoiled, but still double stranded. • NO DNA replication occurs. • Centrioles are replicated. • Cells contain half the chromosome number as the parent cell.

  20. Prophase II • Same as Mitosis Metaphase II • Same as Mitosis Anaphase II • Same as Mitosis Telophase II • Same as Mitosis

  21. Results of Meiosis • 1 parent cell produces 4 daughter cells • Daughter cells are haploid gametes. • Fertilization results form the fusion of 2 haploid gametes to form a diploid zygote.

  22. Spermatogenesis • Sperm cell formation • 4 equal sized gametes form 23 23D 23 46 46D 23 23D 23

  23. Oogenesis • Egg cell formation • 1 large egg + 3 polar bodies (die) 23 23D 46 46D 23 23 23 23D

  24. 46 46 23D 23D 23 23 23 23 Mitosis vs. Meiosis Meiosis Mitosis Zygote Diploid Cells Fertilization Haploid Cells 23 Gametes

  25. Genetic Variations • Sexual reproduction (fertilization) • Meiosis - independent assortment • Meiosis - crossing over • Random Mutations

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