Observation
of permanent slide for mitosis and meiosis
Aim:
To observe the different stages of meiosis using permanent slides
Principle:
Meiosis is a type of cell division in which the number of chromosomes is halved
(from diploid to haploid) in the daughter cells, i.e., the gametes. The
division is completed in two phases, meiosis I and meiosis II. Meiosis I is a
reduction division in which the chromosomes of homologous pairs separate from
each other. Meiosis II is equation division resulting in the formation of four
daughter cells. Stages of meiosis can be observed in a cytological preparation
of the cells of testis tubules or in the pollen mother cells of the anthers of
flower buds.
Requirement: Permanent
slides of meiosis and compound microscope
Procedure: Place
the slide on the stage of the microscope and search for the dividing cells
using lower magnification. When dividing cells are located observe them under
higher magnification.
Observation:
Various stages of meiosis were identified on
the basis of the specific features present in the slide. A significant number
of cells will be in the Interphase.
Leptotene:The
nuclear membrane and nucleolus are not distinctly observable.
Zygotene:
This stage is characterised by the pairing of the homologous chromosomes, which
can be seen as paired chromatin threads (bivalents)
Pachytene:
The chromatin threads get condensed and appear shortened and thick. Pairs of
homologous chromosomes and tetrad can be seen.
Diplotene:
The homologous chromosomes show distinct separation from each other except at
few regions where attachments are seen. These are called chiasmata where
crossing over occurs.
Diakinesis:
Nucleus division can be seen.
Metaphase
I: At this stage, the number of bivalents can be counted.
Chiasmata may still be seen in a few bivalents.
Anaphase
I: This stage can be identified the presence of two chromatids in
each chromosome.
Telophase
I: The chromosomes present at the two poles appear decondensed and
form two distinct nuclei.
Prophase
II: (i) Distinct thread- like chromatin fibers or rod- shaped
chromosome is seen.
Metaphase
II: In the metaphase I of meiosis, a few chiasmata are observed,
where as no chiasmata are observed during metaphase II.
Anaphase
II: The two chromatids of each chromosome after separation appear to
lie at the two poles of the cell
Telophase
II: The separated chromosomes appear de condensed and form nuclei.
Aim: To observe the different stages of mitosis
using permanent slides
Requirement: Permanent
slides of mitosis and compound microscope
Procedure: The permanent slide
was placed on the stage of compound microscope and observed the stages of
mitosis.
Observations:
Various stages
of meiosis were identified on the basis of the specific features present in the
slide.
1. Prophase: In this slide some chromosomes are seen. The
chromosomes are long and scattered. No spindle fiber is seen. Therefore the
stage is Prophase of Mitosis.
2. Metaphase: Some chromosomes are seen in this slide.
Spindle apparatus is seen here. The chromosomes are situated on the equatorial
zone. The chromosomes are divided into chromatids. Therefore this is the Metaphase
of Mitosis.
3. Anaphase: In this slide two sets of chromosomes are
seen. Two sets are present near the two poles. Therefore it is the Anaphase of
Mitosis.
4. Telophase: In this slide two sets of chromosomes are seen. Two sets of chromosomes
are present at two poles. No spindle apparatus is seen. Nuclear membrane is
present surrounding the chromosomes in each pole. Therefore it is the Telophase
of Mitosis.
Note:some content obtained from web source.
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