Meiosis

• Meiosis

  A reduction division that reduces the original chromosome number during cell division (starts with 46 chromosomes and ending with 23 chromosomes)
• Meiosis

  • The daughter cells are gametes (haploid) necessary in the formation of the zygote (2n)
  • One mother cell (2n) produces four daughter cells (n)
  • A process that contributes to genetic variety
  • Makes sperm and egg cells (gametes with 23 chromosomes each)
• Meiosis (interphase)

  When 46 chromosomes duplicate, it remains to be 46 but instead with 92 chromatids as we count by centromeres
• Meiosis I (Prophase I)

  1. Spindle fibers begin to form

  2. The chromosomes condense and thicken

  3. Cross-over occurs where chromosomes line up with their homologous (approximately the same size and same type of genes in the same location) pairs and exchange their genetic information

  4. Makes for what we call recombinant chromosomes (contribute to the variety sibling can have)
• Meiosis I (Metaphase I)

  1. Spindle fibers completely form

  2. Chromosomes are in pairs in the middle of the cell

  3. Two sister chromatids pair its homologous sister chromatids

  4. Crossing over between the homologue pair
• Meiosis I (Anaphase I)


  1. The chromosomes are pulled away by the spindle fibers

  2. Homologues of each pair split and move to the opposite sides, the chromosomes number on each side is half the original number
• Meiosis I (Telophase I)

  1. Pinching of the cell membrane is completed so there are two newly formed nuclei

  2. The nucleolus appear
• Meiosis II (Prophase II)


  1. Have two chromosomes

  2. The spindle fibers begin to form

  3. Has no cross-over like prophase I
• Meiosis II (Metaphase II)

  1. Spindle fibers form completely

  2. The chromosomes align at the center in a single file line
• Meiosis II (Anaphase II)


  The chromatids of each chromosome are pulled apart and move toward opposite sides
• Meiosis II (Telophase II)

  1. The nuclei reforms

  2. The membrane pinches completely to form four cells
• Meiosis (Cytokinesis)

  1. Completely splits the cytoplasm forming gametes (diploids)

  2. When the sperm and egg cell combine, it results in a diploid cell called zygote (fertilized eggs) that will go through mitosis to become a brand new organism
• Nondisjunction is when chromosomes don't separate correctly and cells receive too many or too few chromosomes
• Meiosis

  A) Metaphase II

  B) Interphase

  C) Cytokinesis

  D) Prophase II

  E) Anaphase I