Meiosis in Onion Bud Cell or Grasshopper Testis through Permanent Slides

Aim

To observe the stages of meiosis on onion bud cell or grasshopper testis through permanent slides.

Materials Required

• Permanent slides of meiosis
• Compound Microscope

Procedure

1. Place the slide on the stage of the microscope.
2. Look for dividing cells with lower magnification.

Observations

The different stages of meiosis are observed along on the basis of the following features.

Stages of Meiosis I

Prophase I

In this stage, the chromosomes condense and move towards the centre of the cell. It consists of five different sub-phases:

• Leptotene: The homologous chromosomes replicate.
• Zygotene: Synapsis between homologous chromosomes start.
• Pachytene: The sister chromatids separate but the homologous chromosomes remain attached.
• Diplotene: The two homologous chromosomes migrate apart and disintegrate between the chromosomal arms.
• Diakinesis: The condensation of chromosomes stops at this stage and the chiasmata is clearly visible under an electron microscope. The nucleolus and the nuclear envelop disappear at this stage and the centrosome moves to the equator.

Metaphase I

The homologous chromosomes that contain two different alleles for each gene, line up on the metaphase plate to be separated.

Anaphase I

The separated chromosomes are pulled towards the centrioles on either side of the cell.

Telophase I

The chromosomes are completely pulled apart and new nuclear envelope forms.

Stages of Meiosis II

Prophase II

In this stage, the nuclear envelope disintegrates and centrioles develop.

Metaphase II

The chromosomes line up on the metaphase plate and the chromatids are on either side of the metaphase plate.

Anaphase II

The sister chromatids separate and are known as sister chromosomes.

Telophase II

The cell divides into two and a new nuclear envelope surrounds the chromosomes.

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