Comparison of mitosis and meiosis


Published on

Published in: Science, Technology, Education
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Comparison of mitosis and meiosis

  1. 1. Angela.Bang-Ji Comparison of mitosis and meiosis
  2. 2. What is mitosis and meiosis  Meiosis – cell division that results in cells that have half the normal chromosome number(haploid gametes), it is also called reduction division, specific to create sex cells.  Mitosis – Cell division that results in identical cells, used for growth and repair of organisms.
  3. 3. Cell Cycle : Growth Stage/Interphase  Growth stage also called interphase is where the cell carries out its regular metabolic function and prepares for its next division  Interphase is divided into three phases : G1 phase, S phase and G2 phase.  By the end of interphase, the cell is ready to begins the process of nuclear division: mitosis.
  4. 4. Three phases in Interphase  G1 phase (Growth 1) –The cell goes through rapid growth and metabolic activities.  S phase (Synthesis) –The middle stage of interphase where the cell’s DNA is copied exactly.Which means that the chromatin replicates to create a second identical set of DNA.After the replication, the two identical chromosomes – sister chromatids – are joined at the centromere  G2 phase (Growth 2) – During the replication in S phase, the cell consumed a large amount of energy, therefore this stage allow the cell to regenerate energy for division.As well, the cell manufactures proteins and other molecules to make structures required for division of the nucleus and cell.
  5. 5. 5/6/2014 Sister chromatids are joined by the centromere Diagrams DNA repilcation occur during S phase
  6. 6. Cell division : Mitosis  Four phases in the process of mitosis -Prophase, Metaphase, Anaphase, andTelophase  After the cell has been through all the phases, it enter cytokinesis - the division of the cytoplasm and the organelles into two separate cells.
  7. 7. 5/6/2014 Mitosis : Prophase  Prophase - During this phase, the chromatin condenses into tightly pack chromosomes while the nuclear membrane breaks down, releasing chromosomes into the cytoplasm.  As the nucleolus disppears, pair of cylndrical organelles called centrioles move their way to the opposte poles of the cell  During the separation of the centrioles, a network fibres called the spindle apparatus forms between them
  8. 8. 5/6/2014 Prophase : Diagrams  Spindle fibre is made of microtubules - hollow tubes of proten that facilitate movement of chromosomes within a cell
  9. 9. 5/6/2014 Mitosis : Metaphase  During metaphse, the spindle fibres guide the chromosomes to the centre line of the cell and attach to the centromere of each chromosome.  The chromosomes are lined up in such way that one sister chromatid face one pole and the other sister chromatid face the opposite pole.
  10. 10. 5/6/2014 Metaphase : Diagrams  The chromosomes are lined up horinzontally by the spindle fibres
  11. 11. 5/6/2014 Mitosis : Anaphase  Before anaphase, the chromosomes are line up at the centre line of the cell. During anaphase, the centromere splits apart and the sister chromatids separate from one another.  The spindle fibres from each end still attach to the split centromere, it shortens and pulls the sister chromatid towards its pole.  At the same time, microtubules in the spindle apparatus lengthen and force the poles of the cell away from one another  By the end of anaphase, one complete diploid set of chromosomes has been gathered at each pole and the process of lengthening the microtubules result in a elongated cell
  12. 12. 5/6/2014 Anaphase : Diagrams  Notice the elongated cell
  13. 13. 5/6/2014 Mitosis : Telophase  Final phase of mitosis  The chromatids begin to unwind into longer and less visible strands of chromatin at the opposite pole of the cell  The spindle fibres begin to break down  Nuclear membrane starts to form around each new set of chromosomes and a nucleolus forms within each new nucleus
  14. 14. 5/6/2014 Telophase : Diagrams  Nuclear membranes are formed  The cell will now enter Cytokinesis
  15. 15. 5/6/2014 Cytokinesis  This is the last step of cell division, interphase and mitosis are the process of nuclear division, Cytokinesis is the division of the cytoplasm to complete the creation of two new daughter cells.  In animal cells, an indentation forms in the cell membrane along the cell equator, the indentation deepens until the cell is pinched in two.  This result in the equal divison of the cytoplasm and organelles between the two halves of the cell
  16. 16. 5/6/2014 Cytokinesis : Diagrams  Indentation at the equator  Two daughter cells are formed  End of cell division, the daughter cells are now in G1 phase
  17. 17. 5/6/2014 Meiosis  Other form of cell division is called Meiosis, the process that produces haploid gametes from diploid cells in the ovaries and testes - sex cells -  Two main parts to Meiosis : Reduction division and Recombination  During Meiosis, the four phases that occur in mitosis happens twice, therefore it is called Meiosis I and Meiosis II.
  18. 18. 5/6/2014 Interphase before Meiosis  Like somatic cells, germ cells also goes through the growth and synthesis phases before dividing  Duplicated chromosomes are formed by the end of interphase
  19. 19. 5/6/2014 Meiosis : Prophase I  The homologous chromosomes which contains the same genes but carry different alleles of these genes are align side by side in the this phase.  The alignment of the homologous chromosomes are called synapsis  At synapsis, homologous non-sister chromatids lie side by side.This is a important step that will be later demonstrated in genetic recombination
  20. 20. 5/6/2014 Prophase I : Diagrams  Crossing over between non-siser chromatids may occur.This increases variation in gametes and offspring
  21. 21. 5/6/2014 Metaphase I  A spindle fibre attach to the centromere of each chromosome  A spindle fibre from one pole attaches to one pair of sister chromatids in the tetrad, and a spindle fibre from the opposite pole attach to the other pair of sister chromatids  The spindle fibres guide each tetrad to the equator of the cell, however the chromosomes do not line up in single file as they do in mitosis, instead they line up as homologous pairs.
  22. 22. 5/6/2014 Metaphase 1 : Diagrams  chromosomes line up as homologous pairs.
  23. 23. 5/6/2014 Anaphase I  Similar to Mitosis, during anaphase I in Meiosis, the spindle fibres shorten cause the homologous chromosomes to separate from one another, making their way to opposite poles of the cell  Since the sister chromatids are still held together, the centromeres do not spilt  This result in a single chromosome - made up of two sister chromatids - from each homologous pair moves toward the poles.
  24. 24. 5/6/2014 Anaphase 1 : Diagrams  Result in a single chromosome - made up of two sister chromatids
  25. 25. 5/6/2014 Telophase I  The homologous chromosomes begin to uncoil and the spindle fibres disappear  Each new cell contains one set of sister chromatids and is now haploid
  26. 26. 5/6/2014 Meiosis II  By the end of telophase I, new cells contains one set of sister chromatids are formed and is now haploid  Chromosome replication does not take place before the next phase of meiosis  The process of Meiosis II are similar to the phases of mitosis  Each cell that enters meiosis II is haploid but consists of replicated chromosomes.  At the end of meiosis II, the daughter cells are still haploid but they contain single unreplicated chromosomes.
  27. 27. 5/6/2014 Meiosis II : Diagrams  daughter cells are still haploid but they contain single unreplicated chromosomes.
  28. 28. 5/6/2014 Similarities between Mitosis and Meiosis  Both process go through chromosome replication  Meiosis II is similar to Mitosis  Both Mitosis and Meiosis go through interphase,prophase,metaphase,anaphase and telophase  Both use spndle fibers to separate chromatids from each other
  29. 29. 5/6/2014 Differences between Mitosis and Meiosis  Mitosis produce identical cells, Meiosis produce 4 daughter cells are haploid but they contain single unreplicated chromosomes.  Mitosis is used for growth and repair of organisms, Meiosis is used to reproduce gametes  Four phases in Meiosis I is different from Mitosis, in prophase I synapsis happen, in metaphase I crhomosomes line up as homologous pairs, in anaphase I centromeres do not split result in single chromosome from each homologous pair moves to each pole of the cell, in telophase I daughter cell contain one set of sister chromatid
  30. 30. 5/6/2014 References   e_thing_emily.png       .gif  gif 