Simple Autoclave Diagram

Demonstration of Meiotic Stages in Plant or Animal Material by Observation of Permanent Prepared Slides

Aim: To identify and describe the stages of meiosis by systematic observation of permanent prepared slides under a compound light microscope.

Principle: Meiosis is a special type of cell division that produces four haploid daughter cells from one diploid parent cell. It happens in two successive divisions: meiosis I and meiosis II. The first division is the reductive one, where homologous chromosomes separate. The second division is more like mitosis, where sister chromatids separate. What makes meiosis interesting is the events in prophase I. It is a long and complex stage, divided into five sub-stages: leptotene, zygotene, pachytene, diplotene, and diakinesis. This is where crossing over happens, at the chiasmata.

Requirements:

Permanent slides (pre-prepared, available in the laboratory):

• Permanent slides of meiosis in plant material: commonly Allium cepa (onion) or Lilium (lily) anther sections showing pollen mother cells in various meiotic stages
• OR permanent slides of animal material: commonly testis sections of grasshopper (Schistocerca gregaria or Locusta migratoria) or Drosophila melanogaster which shows clear meiotic figures

Equipment:

• Compound light microscope with 10X, 40X, and 100X (oil immersion) objectives
• Immersion oil (for 100X observation, if needed)
• Lens cleaning tissue and lens cleaning solution
• Stage micrometer (optional, for measuring chromosome size)

For recording observations:

• Drawing sheets or laboratory notebook
• Pencil (HB) for drawing
• Permanent marker for labelling
• Ruler

Procedure:

1. Take the permanent slide carefully from slide box. Hold from edges only.
2. Clean the slide gently using lens paper if dust is present.
3. Place the slide on microscope stage. Fix it properly with stage clips.
4. Start observation under low power objective (10X).
5. Adjust mirror and focus to get clear field.
6. Locate well spread cells in the field. Do not rush here.
7. Switch to high power objective (40X).
8. Focus slowly using fine adjustment knob.
9. Observe different stages like prophase I, metaphase I, anaphase I and telophase I.
10. Try to identify stages based on chromosome arrangement.
11. Note down observations and draw diagrams.

Observation: In permanent slides of Lilium anther or grasshopper testis, cells at various meiotic stages are visible, stained purple to dark violet, with chromosomes appearing as distinct, condensed thread-like or rod-like structures against a lighter cytoplasmic background. In prophase I stages, chiasmata appear as X-shaped connections between paired homologs in diplotene and diakinesis, while metaphase I cells show bivalents clearly aligned at the cell equator.

Result: All stages of meiosis I (leptotene, zygotene, pachytene, diplotene, diakinesis, metaphase I, anaphase I, telophase I) and meiosis II (prophase II through tetrad formation) were successfully identified and distinguished in the permanent prepared slide under a compound light microscope.

Conclusion: Permanent slides offer a very convenient way to study meiosis, particularly because finding actively dividing meiotic material in fresh preparations is timing-dependent and not always practical for a classroom setting.

Note: This protocol is for educational use in standard teaching laboratories. Small variations may occur depending on lab conditions and handling. Results may vary. biologynotes.in cannot take responsibility for any errors, misuse, or results obtained. Always follow proper lab safety and instructor guidance.