Stages of Meiosis

• What type of cell do we start with in meiosis?

  Diploid cell
• How many haploid gametes are produced from meiosis?

  Four haploid gametes
• What happens to chromosomes during meiosis?

  They are separated into individual chromosomes
• How many rounds of nuclear division occur in meiosis?

  Two rounds of nuclear division
• What is separated during meiosis 1?

  Homologous chromosomes
• What is separated during meiosis 2?

  Sister chromatids
• What occurs during interphase before meiosis starts?

  The cell copies chromosomes and organelles
• What is the first stage of meiosis 1?

  Prophase 1
• What happens to chromosomes during prophase 1?

  Chromosomes condense and become visible
• What structure forms when homologous chromosomes link together?

  Bivalent
• What is crossing over?

  Exchanging alleles between homologous chromosomes
• What happens to the nuclear membrane during prophase 1?

  It breaks down
• What is the role of spindle fibers during meiosis?

  To separate chromosomes
• What occurs during anaphase 1?

  Homologous chromosomes move towards opposite poles
• What happens during telophase 1?

  Nuclear membranes reform and chromosomes uncoil
• What type of cells are produced after meiosis 1?

  Haploid cells
• What is the first stage of meiosis 2?

  Prophase 2
• What happens during anaphase 2?

  Centromeres divide and chromatids move apart
• What is the final outcome of meiosis?

  Four genetically different haploid cells
• What is reduction division in meiosis?

  Chromosome number halves during division
• What are the two main sources of genetic variation in meiosis?

  Crossing over and independent assortment
• What is independent assortment?

  Random distribution of maternal and paternal chromosomes
• How many chromosome pairs do human cells have?

  23 chromosome pairs
• How many genetically different gametes can be produced by independent assortment?

  $2^n$ where $n$ is chromosome pairs
• What is the number of genetically different gametes from humans?

  Over 8 million gametes
• How does random fusion of gametes contribute to genetic variation?

  It introduces additional genetic combinations
• What are the stages of meiosis?

  1. Meiosis I:

  • Prophase I
  • Metaphase I
  • Anaphase I
  • Telophase I

  1. Meiosis II:

  • Prophase II
  • Metaphase II
  • Anaphase II
  • Telophase II
• What are the two ways meiosis increases genetic variation?

  • Crossing over
  • Independent assortment of chromosomes
• What is the significance of cytokinesis in meiosis?

  • Divides the cytoplasm
  • Produces haploid cells
• How do crossing over and independent assortment differ in their contribution to genetic variation?

  • Crossing over: exchanges alleles between homologous chromosomes
  • Independent assortment: random distribution of chromosomes