bio

• Meiosis


  A type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells
• Meiosis


  • Sexual reproduction
  • Provides "genetic variation"
• Meiosis


  1. Meiosis I (Reductional division)

  2. Meiosis II (Equational division)
• Meiosis I


  Diploid cells are reduced to haploid
• Meiosis II


  Sister chromatids separate
• Types of cells in organisms that reproduce sexually

  • Somatic Cells (body cells, diploid)
  • Gametes (sex cells, haploid)
• Somatic cells


  Contain the normal number of chromosomes (diploid)
• Gametes


  Contain only 1⁄2 the normal number of chromosomes (haploid)
• Male gamete


  Sperm, produced in the testes
• Female gamete


  Ovum, produced in the ovaries
• Fertilization


  Fusion of a sperm and egg to form a zygote
• Homologous chromosomes


  Pair of chromosomes (maternal and paternal) that are similar in shape and size
• Humans have 23 pairs of homologous chromosomes, 22 pairs of autosomes and 1 pair of sex chromosomes
• Meiosis: Prophase I


  1. Leptotene

  2. Zygotene

  3. Pachytene

  4. Diplotene

  5. Diakinesis
• Crossing-over


  Process by which non sister chromatids exchange genetic segments, increasing genetic variation
• Meiosis: Metaphase I


  Homologous chromosomes move randomly at the metaphase plate
• Meiosis: Anaphase I


  Homologous chromosomes separate and move towards the pole
• Meiosis: Telophase I


  Each pole has a haploid set of chromosomes, cell membrane starts to reappear, cytokinesis occurs
• Meiosis


  A type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells
• Meiosis: Prophase II


  Chromosomes condensed again, nuclear membrane starts to disappear, spindle fibers begin to form
• Meiosis: Metaphase II


  Chromosomes align at the metaphase plate, spindle fibers attached to kinetochores, sister chromatids prepare to separate
• Meiosis


  • Sexual reproduction
  • Provides "genetic variation"
• Meiosis: Anaphase II


  Sister chromatids move to the opposite poles
• Meiosis: Telophase II


  Chromosomes start to uncoil, nuclear membranes start to reappear, cytokinesis splits the cells into 4 haploid cells
• Meiosis


  1. Meiosis I (Reductional division)

  2. Meiosis II (Equational division)
• Karl Lohmann discovered ATP from extracts of muscles and livers


  1929
• ATP


  Energy used by all cells (energy currency of life), Adenosine TriPhosphate, organic molecule containing high-energy phosphate bonds
• Meiosis I


  Diploid cells are reduced to haploid
• How we get energy from ATP


  By breaking the high-energy bonds between the last two phosphates in ATP
• Meiosis II


  Sister chromatids separate
• All cells have a small storage of highly charged ATP molecules, specifically located in the cytoplasm of the cell
• Types of cells in organisms that reproduce sexually

  • Somatic Cells (body cells, diploid)
  • Gametes (sex cells, haploid)
• Hydrolysis


  The process of breaking down ATP
• Somatic cells


  Contain the normal number of chromosomes (diploid)
• We need an enzyme to break down ATP
• Reverse of breaking down ATP

  ATP Synthase enzyme is used
• Gametes


  Contain only 1⁄2 the normal number of chromosomes (haploid)
• Endergonic reaction


  Energy is the basic requirement, nonspontaneous, usually occur in organisms to synthesize complex molecules
• Male gamete


  Sperm, produced in the testes
• Exergonic reaction


  Spontaneous, favorable chemical reactions where products are at lower energy level than reactants, release free energy