BIOL1102 Week 6

• Mitosis


  Cell division process that distributes identical genetic material to daughter cells

  
• Meiosis


  Cell division process that produces genetically distinct daughter cells

  
• Cell division


  • Enables asexual reproduction
  • Enables growth and development
  • Enables tissue renewal
• Genetic material


  DNA molecules packaged into chromosomes

  
• Gene


  Segment of DNA that codes for a specific protein
• Genome


  Complete set of genetic material in an organism
• Chromatin


  Complex of DNA and proteins that form chromosomes

  
• Chromosome


  • Region of highly repeated DNA
  • Where the kinetochores assemble
  • Where sister chromatids are held together

  
• Human cell division takes approximately 24 hours
• The average adult human has 37 trillion cells
• Over an average life span, cells in our body regenerate by dividing about 50 to 70 times
• Epithelial cells are one of the fastest dividing cells
• Human cell division takes approx. 24 hrs
• Average adult human has 37 trillion cells
• Mitosis


  The process of cell division that produces two genetically identical daughter cells

  
• Meiosis


  The process of cell division that produces four genetically distinct daughter cells

  
• The cell cycle


  1. G1 phase

  2. S phase

  3. G2 phase

  4. Mitotic phase
• G1 phase


  • First gap phase, follows completion of mitotic phase, longest part of cell cycle
• Interphase


  • Intense metabolic activity and growth
• S phase


  • DNA synthesis, when DNA replication occurs, chromosomes are duplicated

  
• G2 phase


  • Cell size increases, final preparations for mitosis
• Mitotic phase


  • In mitosis, chromosomes separate into daughter nuclei, cytokinesis divides cytoplasm, producing two daughter cells

  
• Microtubules are required for chromosome segregation

  
• Cytokinesis


  The division of the cytoplasm to form two separate daughter cells

  
• Cytokinesis is different in animal and plant cells
• Prokaryotic cells divide by binary fission

  
• Binary fission


  1. DNA replication begins at origin of replication

  2. Cell elongation occurs during replication

  3. Plasma membrane pinched inwards by tubulin-like protein

  4. New cell wall forms

  5. Two daughter cells with identical genetic information

  
• Binary fission


  Division in half
• Single-celled eukaryotes also reproduce by binary fission

  
• Meiosis leads to variation

  
• Learning outcomes


  • Describe the microscopic structure of cells
  • Examine the nature and flow of genetic information
  • Explain how complex organisms develop from a single cell
• Lecture learning outcomes


  • Describe sexual life cycles in different organisms
  • Understand how meiosis leads to variation
  • Compare and contrast mitosis and meiosis
• Offspring are exact genetic copies of parent in asexual reproduction
• Examples of asexual reproduction in multicellular organisms

  • Hydra
  • Redwoods
• Offspring vary genetically from siblings and parents in sexual reproduction
• Human life cycle


  • Meiosis occurs in the gonads
  • Gametes produced are haploid
  • Fertilisation results in a diploid zygote
• Homologous chromosomes


  • 22 pairs of autosomes
  • 1 pair of sex chromosomes

  
• Humans normally have 23 pairs of chromosomes in each somatic cell

  
• Homologous chromosomes


  Chromosomes that were inherited from the same parent and carry the same alleles
• Composition of human chromosomes

  • 22 pairs of autosomes
  • 1 pair of sex chromosomes