Lecture Notes: Mitosis vs. Meiosis

Introduction

• Vocabulary in biology can sound similar: Chromosome, Chromatid, Chromatin, Transcription, Translation, Mitosis, Meiosis.
• Importance of understanding similarities and differences between mitosis and meiosis.
• Aim: Provide a side-by-side comparison of mitosis and meiosis.

Key Concepts

• Mitosis: Process that results in body cells.
• Meiosis: Process that results in gametes (sperm and egg cells).
• Both processes start with a diploid cell (2n).
• Interphase precedes both processes and involves chromosome duplication.

Chromosome Details

• Humans have 46 chromosomes (23 from each parent).
• Chromosomes duplicate during interphase, resulting in 92 chromatids.
• Illustrations often show 6 chromosomes for simplicity.
• Some insects, like mosquitoes, actually have 6 chromosomes.

Stages of Mitosis and Meiosis

• PMAT Acronym: Prophase, Metaphase, Anaphase, Telophase.
• Mitosis and meiosis go through these stages, with meiosis undergoing them twice.

Mitosis

• Prophase: Chromosomes condense and become visible.
• Metaphase: Chromosomes line up in the middle of the cell.
• Anaphase: Chromatids are pulled away to opposite sides.
• Telophase: New nuclei form at opposite ends, followed by cytokinesis.
• End Result: Two identical, diploid cells (46 chromosomes each in humans).

Meiosis

• Prophase I: Chromosomes condense and match with homologous pairs; crossing over occurs.
• Metaphase I: Chromosomes align in pairs at the cell's middle.
• Anaphase I: Homologous chromosomes are pulled away.
• Telophase I: New nuclei form, cytokinesis completes cell division.
• Prophase II: Chromosomes condense again, no homologous pairs.
• Metaphase II: Chromosomes line up in a single file line.
• Anaphase II: Chromatids are pulled away.
• Telophase II: New nuclei form, cytokinesis follows.
• End Result: Four non-identical haploid cells (23 chromosomes each in humans).

Significance

• Mitosis: Supports growth and cell replacement.
• Meiosis: Produces gametes for sexual reproduction.
• Sperm and egg union leads to a zygote, a diploid cell that develops into a new organism.

Conclusion

• The comparison highlights the distinction in outcomes and processes between mitosis and meiosis.
• Importance of staying curious and exploring further details in cellular biology.