L54: Meiosis

• Who is the professor of the lecture series?

  Professor Eric B Holub
• What is the focus of Lecture 54?

  Meiosis - Shuffling the genetic deck
• What is the focus of Lecture 55?

  Mendel’s legacy - The seed of how to do great science
• What is the focus of Lecture 56?

  Recombination - Birth of Linkage Mapping
• What is the chromosome structure of a human female?

  44A XX
• What are polytene chromosomes and where are they found?

  They are found in Drosophila salivary glands
• Why do polytene chromosomes arise?

  Because replicated DNA strands do not separate
• What do visible bands on polytene chromosomes provide?

  High resolution physical map position
• What is the era of genome sequence associated with?

  Dictyostelium discoideum, Mus musculus, Homo sapiens
• What is the link to the movie on mitosis?


  https://www.youtube.com/watch?v=L61Gp_d7evo
• What are the two types of cell division?

  • Mitosis: Generates two identical daughter cells
  • Meiosis: Generates four genetically distinct daughter cells
• What is the purpose of mitosis?

  Multiplication, growth & tissue maintenance
• What is the purpose of meiosis?

  Sexual reproduction and genetic shuffling
• What happens during interphase?

  Chromosomes and organelles replicate
• What occurs during prophase of mitosis?

  Chromosomes start condensing and nuclear membrane breaks down
• What is the role of the spindle during mitosis?

  Attaches to centromeres and helps separate chromosomes
• What happens during metaphase of mitosis?

  Centromeres align at the equator
• What occurs during anaphase of mitosis?

  Chromosomes migrate to opposite poles
• What happens during telophase of mitosis?

  Nuclear membrane reforms and chromosomes decondense
• What is cytokinesis?

  Division of the cytoplasm to form two cells
• What destroys sister chromatid cohesion during anaphase?

  Separase breaks down cohesin protein
• What is the summary of mitosis?

  • Prophase: Chromosomes condense, spindle forms
  • Metaphase: Chromosomes align at equator
  • Anaphase: Chromosomes separate to poles
  • Telophase: Nuclear membrane reforms, chromosomes decondense
  • Cytokinesis: Cytoplasm divides into two cells
• What is the main outcome of meiosis?

  Four genetically distinct haploid cells
• What occurs during prophase I of meiosis?

  Homologous chromosomes align and form synaptonemal complex
• What is the significance of chiasmata in meiosis?

  They are sites for crossing-over between non-sister chromatids
• What happens during telophase I of meiosis?

  Haploid cells have formed after division
• What is the outcome of meiosis II?

  Four genetically distinct haploid cells
• What are the five stages of prophase I in meiosis?

  1. Leptotene: Chromosomes condense, homolog pairing begins
  2. Zygotene: Synaptonemal complex forms, bivalents appear
  3. Pachytene: Crossing-over occurs, tetrads form
  4. Diplotene: Chiasmata visible, sister chromatids separate
  5. Diakinesis: Chromosomes repel, nuclear membrane disappears
• What is the function of the synaptonemal complex?

  Facilitates recombination and prevents entanglement
• How much DNA does a human cell contain?

  Over two metres of DNA
• What is the summary of meiosis I?

  • Maintains ploidy level for sexual reproduction
  • Genetic shuffling occurs via independent assortment and crossing-over
• What is the summary of meiosis II?

  • Sister chromatids separate
  • Results in four genetically distinct haploid cells
• What is the total number of possible combinations of haploid gametes in meiosis I?

  2$^{10}$
• What is the chromosome structure of Arabidopsis?

  n = 5
• What is the chromosome structure of Agave?

  n = 30
• What is the chromosome structure of a mouse?

  n = 20
• What is the chromosome structure of a human?

  n = 23
• What are the components of chromosome structure?

  Telomeres, centromere, and kinetochore
• What is the role of telomeres in chromosomes?

  Maintain length and protect chromosome ends
• What is the function of the kinetochore?

  Spindle attachment during cell division