Mitosis and Meiosis

• Mitosis - A type of cell division that results in two genetically identical daughter cells.
• Meiosis - A type of cell division that produces four haploid gametes from one diploid parent cell.
• Mitosis is a fundamental process during growth and tissue repair as well asexual reproduction.
• Meiosis occurs only in the reproductive organs, resulting in genetic variation through sexual reproduction.
• The stages of mitosis are prophase, metaphase, anaphase, telophase, and cytokinesis.
• 4 STAGES OF MITOSIS

  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase
• Interphase - This is where the cell grows, replicates its chromosomes or the DNA,  and prepares the cell for cell division.
• Prophase - The chromosomes are thicker and shorter because of repeated coiling; The two chromatids are still attached the centromere
• Metaphase - Chromosomes line up at the equatorial plate (metaphase plate) along with the spindle fibers that attach to the kinetochores on the centromeres of the sister chromatids.
• Cytokinesis - A cleavage furrow forms between the daughter cells, dividing the cytoplasm into two equal parts.
• Anaphase - Sister chromatids separate from one another due to the contraction of microtubules pulling them apart; The centromere is dividing.
• Anaphase - Spindle fibers begin to contract  and become shorter. Chromosomes move to opposite poles of the cell.
• Prophase - The nuclear membrane and nuclei breakdown or dissolving but in some cases they may still be present.
• Telophase -  The chromosomes   are   now   at   opposite poles   of   the   spindle; The new nuclear membrane are formed around them while the spindle fiber disappears.
• Cytokinesis - Cytoplasmic division, splitting the cell into two.
• Cytokinesis is a Cytoplasmic division, splitting the cell into two.
• what stage is this?

  A) prophase

  
• MITOSIS CYCLE

  A) interphase

  B) prophase

  C) metaphase

  D) anaphase

  E) telophase

  F) cytokinesis

  
• Meiosis is a type of cell division that produces gametes, or sex/germ cells, with half the number of chromosomes of the original cell.
• spermatogenesis - the process of the formation of matured sperm cells
• oogenesis - the process of formation of egg cell from the primary oocyte to one of whom egg cell is produced and three of them become polar bodies
• Meiosis is from Greek word “meioun” which means “to make smaller.”
• gametogenesis - the process by which gametes, or germ cells, are produced in an organism.
• TWO STEP DIVISION OF MEIOSIS

  1. Meiosis I

  2. Meiosis II
• Meiosis I - Separates the pair of homologous chromosomes and reduces the diploid cell (2N) to haploid(N)
• MEIOSIS IS A REDUCTIONAL DIVISION because it produces four genetically different haploid cells with half the number of chromosomes as the parental cell.
• Meiosis II - The Sister chromatids separate and four daughter cells are formed, each carrying haploid number of chromosome
• Prophase I - The homologous chromosome pair to form a tetrad and exchange DNA to form recombinant chromosomes.
• TWO EVENTS IN PROPHASE I

  Synapsis

  Crossing Over
• Synapsis - the process of pairing of the homologous chromosomes
• Crossing Over - the process of exchanging genetic material between homologous chromosomes
• TEO EVENTS IN PROPHASE I

  A) sypnasis

  B) crossing over

  
• FIVE SUB-PHASES OF PROPHASE I

  Laptotene

  Zygotene

  Pachytene

  Diplotene

  Diakinesis
• laptotene - a sub-phase prophase I where the chromosomes starts to condense
• zygotene - a sub-phase prophase I where the homologous pairs are aligned side by side along their length, forming bivalents; where Synapsis occurs to form tetrad (pairs of chromosomes consisting of four chromatids).
• pachytene - a sub-phase of prophase I crossing over occur forming chiasma (the point of contact of crossing over)
• diplotene - a sub-phase prophase I where homologous

  chromosomes begin to separate but remain attached by chiasmata.
• diakinesis - a sub-phase prophase I wherehomologous chromosome pair completely separated from one another.
• metaphase I -a stage of meiosis I where Homologous chromosomes line up at equatorial plate
• ANAPHASE I - a stage of meiosis I where Homologous chromosomes move towards opposite poles.