Meiosis in Onion Bud Cell or Grasshopper Testis through Permanent Slide

Meiosis is a type of cell division that occurs in the germ cells of sexually reproducing organisms and is utilized to produce gametes such as sperm and egg cells. There are two rounds of division in meiosis that produce four cells, with a single copy of each chromosome. The daughter nuclei formed as a result of this division undergo a chromosomal number change from diploid to monoploid or haploid.

Due to their availability, relatively large, and fewer chromosomes, grasshoppers are suitable materials for studying various meiotic stages of spermatogenesis.

Also Read: Cell Biology

Key Terms: Meiosis, Meiosis in Onion, Grasshopper Testis, Onion Bud Cells, Chromosomes, Prophase, Metaphase, Anaphase, Telophase

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Aim

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To closely observe through permanent slides the processes of meiosis on onion bud cells or grasshopper testis.

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Instrument & Material Required

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1. Meiosis permanent Slides
2. Compound Microscope

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Squash Preparation

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1. One or both testicular lobes are removed.
2. Next, the removed testis is placed on a freshly taken glass slide.
3. One or two drops of acetocarmine stain are added to the slide.
4. The teste lobes are chopped into little pieces using a sharp blade and maintained for 10 minutes.
5. The slide is to be covered carefully using a coverslip. This prevents the formation of air bubbles.
6. The slide is gently warmed. Two layers of filter papers are kept such that the slide is sandwiched between them.
7. The extra stain is removed from the sides of the coverslip by pressing the material with a fingertip.
8. The microscope is used to examine the slide.

Also Read: Simple Microscope

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Procedure

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1. The insects are chloroformed or euthanized before being dissected in saline water on a dissecting tray. 
2. The testis is located in the front half of the abdomen, in the dorsal location, and can be easily found by making a dorsal, longitudinal abdominal cut.
3. Soaking of the testis in the fixative is mandatory for a minimum of 5 minutes.
4. A clean slide is taken and a small drop of the stain is placed in the center of the slide. 
5. 3 to 4 testis follicles are removed from the fixative, and excess moisture is eliminated with a blotting paper.
6. This is left undisturbed for 3 to 5 minutes in the stain. 
7. By firmly tapping the follicles with a glass rod, the follicles are to be broken. 
8. Any large pieces of tissue are to be removed and the item is covered with a clean cover slip.
9. The slides for the onion bud cells are prepared.
10. The slides are now placed on the stage of the microscope.
11. Cells that are dividing at reduced magnification are closely observed.

Note: If necessary, the testis can be stored in a fixative solution or 70% ethanol for future use

Schematic of the Stages of Meiosis

Also Read: Stages of Meiosis

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Observations

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The following characteristics are used to distinguish the different stages of meiosis:

Meiosis I

• The chromosomes compress and migrate towards the cell center during Prophase I. It is divided into five sub-phases:
  1. Leptotene: The homologous chromosomes replicate here.
  2. Zygotene: Synapsis between homologous chromosomes begins here.
  3. Pachytene: Sister chromatids split, while homologous chromosomes stay linked here.
  4. Diplotene: The two homologous chromosomes separate and disintegrate between the chromosomal arms as they migrate apart.
  5. Diakinesis: Chromosomal condensation ceases, and the chiasmata can be observed under an electron microscope. The nucleolus and nuclear envelopes vanish, and the centrosome travels to the equator.
• The homologous chromosomes with two distinct alleles for each gene line up on the metaphase plate to be separated in Metaphase I.
• The split chromosomes are dragged towards the centrioles on either side of the cell during Anaphase I.
• The chromosomes are entirely torn apart in Telophase I, and a new nuclear envelope develops.

Meiosis II

• The nuclear envelope disintegrates and centrioles form during Prophase II.
• The chromosomes line up on the metaphase plate in Metaphase II, and the chromatids are on each side of the metaphase plate.
• Sister chromosomes are formed when sister chromatids split during Anaphase II.
• The cell divides into two during Telophase II, and a new nuclear envelope surrounds the chromosomes.

Meiosis in Grasshopper Testis under Microscope

(1. Interphase 2. Leptotene 3. Zygotene 4. Pachytene 5. Diplotene 6. Diakinese 7.Metaphase-I 8. Anaphase-I 9. Teleophase-I 10. Prophase-II 11. Metaphase-II 12. Anaphase-II 13. Telophase-II 14. Spermatids)

Also Read: Mitosis Stages

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Things to Remember

• Meiosis: Cell division in the germ cells for sexually producing living organism.
• Meiosis produces gametes like sperms and egg cells.
• In meiosis, there are 2 rounds producing 4 cells with each having a copy of the chromosome.
• Prophase I, Metaphase I, Anaphase I, and Telophase I are the different stages in Meiosis I.
• Prophase II, Metaphase II, Anaphase II, and Telophase II are the different stages in Meiosis II.
• Prophase 1 is sub-divided into 5 phases: Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis. 

Also Read: Equational Division of Cells