Lecture Notes: Mitosis and Meiosis Comparison

Key Vocabulary

• Chromosome: Structure of nucleic acids and protein found in the nucleus, carrying genetic information.
• Chromatid: Each of the two thread-like strands into which a chromosome divides during cell division.
• Chromatin: Material of which chromosomes are composed; consists of protein, RNA, and DNA.
• Transcription: Process of copying a segment of DNA into RNA.
• Translation: Process of translating the sequence of mRNA to a sequence of amino acids.
• Mitosis: Type of cell division that results in two daughter cells, each with the same number and kind of chromosomes as the parent nucleus.
• Meiosis: Type of cell division that results in four daughter cells, each with half the number of chromosomes of the parent cell.

Introduction

• Focus: Side-by-side comparison of mitosis and meiosis.
• Purpose: Understanding similarities, differences, and significance of mitosis and meiosis.
• Visual Aid: Split screen presentation for comparison.

Starting Conditions

• Mitosis and Meiosis: Starts with a diploid cell (2n).
• Human chromosomes: 46 total (23 from each parent).
• Interphase: Prepares for division by duplicating chromosomes (46 chromosomes, 92 chromatids).
  • Note: Not part of mitosis/meiosis but crucial for chromosome duplication.

Stages of Mitosis (PMAT)

1. Prophase
   • Key Event: Chromosomes condense and become visible.
2. Metaphase
   • Key Event: Chromosomes align in the middle of the cell (single file).
3. Anaphase
   • Key Event: Chromatids are pulled apart to opposite sides of the cell.
4. Telophase
   • Key Event: Chromosomes are at opposite ends; new nuclei form.
   • Cytokinesis: Division of cytoplasm, resulting in two identical diploid cells.

Stages of Meiosis (PMAT I and II)

• Note: Meiosis involves two rounds of division.

Meiosis I

1. Prophase I
   • Key Event: Homologous chromosomes pair and crossing over occurs.
2. Metaphase I
   • Key Event: Chromosome pairs align in the middle.
3. Anaphase I
   • Key Event: Chromosomes (not chromatids) are pulled apart.
4. Telophase I
   • Key Event: Chromosomes at opposite ends; new nuclei form.
   • Cytokinesis: Resulting in two non-identical cells.

Meiosis II

1. Prophase II
   • Key Event: Chromosomes condense in two cells.
2. Metaphase II
   • Key Event: Chromosomes line up in single file.
3. Anaphase II
   • Key Event: Chromatids are pulled apart.
4. Telophase II
   • Key Event: Chromosomes at opposite ends; new nuclei form.
   • Cytokinesis: Results in four non-identical haploid gametes.

Significance of Meiosis

• Outcome: Four non-identical haploid cells (gametes).
• Human cells: 23 chromosomes each.
• Reproduction: Fusion of sperm and egg forms a diploid zygote.

Conclusion

• Final Thought: Understanding these processes explains cell division and growth.
• Encouragement: Stay curious about biological processes.