Meiosis

• What are sex cells in animals and plants called?

  Gametes
• What are the gametes in animals?

  Egg and sperm
• Where are egg cells produced in mammals?

  In the ovaries
• Where are sperm cells produced?

  In the testes
• What is the role of mitochondria in gametes?

  They provide energy
• Why are enzymes present in sperm cells?

  To digest the egg cell membrane
• What is meiosis essential for?

  Sexual reproduction
• How many haploid cells does meiosis produce?

  4 haploid cells
• How many nuclear divisions are involved in meiosis?

  2 nuclear divisions
• What does meiosis distribute to each daughter cell?

  One of each homologous pair of chromosomes
• What leads to variation in meiosis?

  Reduction and fusion of gametes, crossing over, and independent assortment
• What is the result of crossing over during prophase 1?

  A new combination of genes on one chromosome
• What is the exchange of genetic material between non-sister chromatids called?

  Crossing over
• What happens during independent assortment at metaphase?

  Homologous pairs of chromosomes align randomly
• What is produced at the end of meiosis I?

  Two cells, each containing one full set of genes
• What happens during meiosis II?

  The pairs of chromatids are separated, forming two more cells
• What is the result of meiosis?

  4 haploid daughter cells
• What is the significance of crossing over and independent assortment in meiosis?

  They produce genetically different cells
• What occurs during prophase 1 of meiosis?

  Chromosomes condense and homologous chromosomes pair up
• What happens during metaphase 1 of meiosis?

  Homologous pairs of chromosomes assemble along the metaphase plate
• What is independent assortment?

  The random alignment of homologous pairs along the equator of the spindle
• What happens during anaphase 1?

  Homologous chromosomes are pulled to opposite poles
• What is chiasmata?

  The point where chromatids break and rejoin during crossing over
• What happens during telophase 1?

  Chromosomes assemble at the poles and the nuclear membrane reforms
• What occurs during prophase 2?

  Chromosomes condense and become visible again
• What happens during metaphase 2?

  Individual chromosomes assemble on the metaphase plate
• What occurs during anaphase 2?

  Chromatids are pulled to opposite poles after division of centromeres
• What happens during telophase 2?

  Chromatids assemble at the poles and the nuclear envelope reforms
• What is the result of cytokinesis in meiosis?

  Formation of 4 genetically different haploid daughter cells
• What are the key stages of meiosis I?

  1. Prophase I: Chromosomes condense, homologous chromosomes pair up, crossing over occurs.
  2. Metaphase I: Homologous pairs align along the metaphase plate.
  3. Anaphase I: Homologous chromosomes are pulled to opposite poles.
  4. Telophase I: Chromosomes assemble at the poles, nuclear membrane reforms.
• What are the key stages of meiosis II?

  1. Prophase II: Chromosomes condense and become visible again.
  2. Metaphase II: Individual chromosomes assemble on the metaphase plate.
  3. Anaphase II: Chromatids are pulled to opposite poles.
  4. Telophase II: Chromatids assemble at the poles, nuclear envelope reforms, cytokinesis occurs.
• What are the three mechanisms that lead to genetic variation in meiosis?

  • Reduction and fusion of gametes
  • Crossing over during prophase I
  • Independent assortment during metaphase I
• What is the significance of genetic variation in offspring?

  • Increases adaptability to changing environments
  • Enhances survival and reproduction
  • Contributes to evolution
• When does independent assortment occur?

  Metaphase 1
• when does crossing over occur?

  prophase 1