chapter 4 - reproduction

• Cell division is the process where cells replicate themselves

  • prokaryotes - binary fission
  • eukaryotes - much more complex reproductive process
• Cell cycle

  The series of events that take place in a cell leading to its division and duplication
• G1 Phase(presynthetic gap)


  Cell grows and prepares to replicate DNA, gathers energy and builds organelles
• S phase(synthesis)


  DNA replication occurs, each chromosome duplicates forming 2 identical chromatids
• G2 Phase(photosynthetic gap)


  Cell checks for errors in DNA replication, completes growth, prepares for division
• M Phase (mitosis)

  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• Prophase

  Chromosomes condense, nuclear membrane breaks down, spindle fibers form
• Metaphase

  Chromosomes align along center, spindle fibers attach to them
• Anaphase

  Sister chromatids separate and move to opposite ends of the cell
• Telophase

  New nuclear membrane forms around each set of chromosomes, uncoil and divide
• Cytokinesis

  Cell splits into 2 daughter cells, each with its own set of chromosomes and organelles
• Asexual reproduction

  Production of offspring from the genetic material of a single parent
• Binary fission

  Simple form of reproduction found in prokaryotes
• Binary fission process

  1. Organism duplicates DNA

  2. Grows larger

  3. Splits into 2 with each organism receiving a copy of DNA
• Budding


  Reproduction where new organism grows as outgrowth from parent organism
• Regeneration

  Ability to regrow lost or damaged body parts, more limited in higher organisms
• Parthenogenesis

  Organism develops from unfertilized egg, rare in higher organisms naturally, can be induced in lab setting
• Sexual reproduction

  Meiosis produces gametes (sperm and egg cells)
• Meiosis

  1. Meiosis I

  2. Meiosis II
• Meiosis I

  1. Prophase I

  2. Metaphase I

  3. Anaphase I

  4. Telophase I
• Prophase I

  Chromosomes condense and pair up, cross over
• Metaphase I

  Homologous chromosome pairs align at metaphase plate, attached to spindle fibers
• Anaphase I


  Homologous chromosomes separate and move to opposite ends, halving chromosome number
• Telophase I

  Nuclear membranes form around separated chromosomes, dividing cell into 2 haploid daughter cells, each with 2 sister chromatids
• Interkinesis

  Short resting phase between meiosis I and meiosis II
• Meiosis II

  1. Prophase II

  2. Metaphase II

  3. Anaphase II

  4. Telophase II
• Prophase II

  Spindle fibers form, centrioles move to opposite ends
• Metaphase II

  Chromosomes line up along metaphase plate, spindle fibers attaching to centromeres
• Anaphase II

  Sister chromatids separate and move to opposite poles
• Telophase II

  Nuclear membranes form around chromosomes, cytokinesis divides cell into 2 daughter cells, resulting in 4 haploid gametes