Meiosis II Lecture Notes

Overview

• Meiosis II follows after the completion of Meiosis I.
• There may be an Interphase II (a rest period) depending on cell type and species.

Meiosis II Phases

Prophase II

• Begins after Meiosis I.
• Key Events:
  • Nuclear envelope dissolves.
  • Chromosomes condense into a denser form.
  • Centrosomes duplicate and begin migrating to opposite ends of the cell.

Metaphase II

• Centrosomes have fully migrated to the poles.
• Nuclear membrane disappears.
• Dense chromosomes line up along the equator of the cell.
  • Microtubules attach to chromosomes at kinetochores and push centrosomes apart.

Anaphase II

• Sister chromatids are pulled apart and become daughter chromosomes, unlike Anaphase I in Meiosis.
• Microtubules, with the help of motor proteins, move chromosomes to opposite ends of the cell.

Telophase II

• Cells transition from two to four cells.
• Key Events:
  • Chromosomes start to unravel into chromatin form.
  • Nuclear envelope reforms.
  • Microtubules dissolve.
  • Cytokinesis occurs, resulting in four haploid cells.

Key Concepts

• Meiosis II is similar to mitosis as it preserves the number of chromosomes.
• Starts and ends with a haploid number of chromosomes.
• Resulting cells are gametes, ready for fertilization.
• Each gamete has two chromosomes, not homologous, coding for different genes.
• During fertilization, these gametes can create a diploid set of chromosomes, enabling sexual reproduction.