Biology

• Meiosis


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

  
• Meiosis


  • Provides "genetic variation"
  • Has 2 divisions
• Meiosis I (Reductional division)


  Diploid cell is reduced to haploid
• Meiosis II (Equational division)


  Sister chromatids separate
• Organisms that reproduce Sexually


  • Made up of two different types of cells
• Somatic Cells


  "Body" cells and contain the normal number of chromosomes (Diploid number)
• Gametes


  "Sex" cells and contain only 1/2 the normal number of chromosomes (Haploid number)
• n


  Number of chromosomes in the set
• 2n


  2 chromosomes in the set
• Polyploid


  Cells have more than two chromosomes per set
• Male Gamete

  Sperm, produced in the Testes
• Female Gamete


  Ovum (ova), produced in the Ovaries
• Fertilization


  The fusion of a sperm and egg to form a zygote
• Zygote


  A fertilized egg
• Homologous Chromosomes


  Pair of chromosomes (maternal and paternal) that are similar in shape and size
• Homologous Chromosomes


  • Carry genes controlling the same inherited traits
  • Each locus (position of a gene) is in the same position on homologues
  • Humans have 23 pairs of homologous chromosomes
• Meiosis: PROPHASE I


  1. Leptotene

  2. Zygotene

  3. Pachytene

  4. Diplotene

  5. Diakinesis

  
• Leptotene


  Chromatin condensed and chromosomes appear
• Zygotene


  Synapsis starts - close pairing of homologous chromosomes due to synaptonemal complex
• Pachytene


  Synapsis is complete, Crossing-over takes place
• Crossing Over


  Creates variation (diversity) in the offspring's traits
• Diplotene


  Synaptonemal complex starts to dissolve and homologous chromosomes start to separate
• Diakinesis


  Homologous chromosomes continue to separate and the chiasmata undergo terminalization
• 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 now has haploid set of chromosomes, cell membrane starts to reappear, Cytokinesis occurs and two haploid daughter cells are formed

  
• Interkinesis


  Brief resting period between Telophase I and Prophase II
• Meiosis: PROPHASE II


  Chromosomes become condensed again, Nuclear membrane starts to disappear, Spindle fibers begin to form
• Meiosis: METAPHASE II


  Chromosomes align at the metaphase plate, Spindle fibers are attached to kinetochores, Sister chromatids prepare to separate

  
• Meiosis: ANAPHASE II


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


  Chromosomes start to uncoil, Nuclear membranes start to reappear, Cytokinesis finally splits the cells, producing 4 haploid cells
• Metabolic reactions and energy transformations


  Processes by which organisms use energy to sustain life
• All organisms continue to live because of energy
• ATP


  The energy currency of life that controls the amount and timing of energy to be used and released within cells
• ATP


  • Vital for many chemical reactions to occur, some of which are done to replace lost molecules
• Karl Lohmann discovered ATP from extracts of muscles and livers


  1929
• ATP


  Adenosine TriPhosphate, an organic molecule containing high-energy phosphate bonds

  
• Getting energy from ATP

  Breaking the high-energy bonds between the last two phosphates in ATP
• Hydrolysis


  The process of breaking down ATP by adding water
• Making ATP


  The reverse of the process of breaking down ATP, using an enzyme