- Onion flower
- Acetocarmine stain
- Glass slides
- Cover slips
- blotting paper
- Select appropriate flower buds of different size from the inflorescence.
- Fix them in Carnoy’s fluid, which is used as fixative.
- Take a preserved flower bud and place it on a glass slide.
- Separate the anthers and discard the other parts of the bud.
- Put 1 or 2 drops of acetocarmine stain and squash the anthers.
- Leave the material in the stain for 5 minutes.
- Place a cover slip over them and tap it gently with a needle or pencil.
- Warm it slightly over the flame of a spirit lamp.
- Put a piece of blotting paper on the cover slip and apply uniform pressure
with your thumb.
- Observe the slide under the microscope for different meiotic stages.
Before under going in meiosis-I, each cell will remain in an interphase, during
which the genetic materials are duplicated due to active DNA replication.
In the first meiotic division, production in the chromosome number occurs
without separation of chromatids. Prophase is the longest phase and has 5
Chromosomes appear as long threadlike structure interwoven together.
Chromosomes display a beaded appearance and are called chromomeres. Ends
of chromosomes are drawn toward nuclear membrane near the centriole. In
some plants, chromosomes may form synthetic knots.
The homologous chromosomes pair with one another, gene by gene, over the
entire length of the chromosomes. The pairing of the homologous chromosomes
is called synapsis. Each pair of homologous chromosomes is known as bivalent.
Each paired chromosomes become shorter and thicker than in earlier substages
and splits into 2 sister chromatids except at the region of the centromere. As
a result of the longitudinal division of each homologous chromosome into
chromatids, there are 4 group of chromatids in the nucleus parallel to each
other, called tetrads.
During the diplotene stage, chiasmata appear to move towards the ends of the
synapsed chromosomes in the process of terminalization. Repulsion of
homologous chiasmata are very clear in pachytene because of the increased
condensation of the chromosomes.
The chromosomes begin to coil, and so become shorter and thicker. Terminalization
is completed. The nucleolus detaches from the nucleolar organizer and disappears
completely. The nuclei envelope starts to degenerate and spindle formation is well
The bivalents orient themselves at random on the equatorial plate. The centromere
of each chromosome of a terminalized tetrad is directed toward the opposite
poles. The chromosomal microtubular spindle fibers remain attached, with the
centromeres and homologous chromosomes ready to separate.
It is characterized by the separation of whole chromosomes of each homologous
pair (tetrad), so that each pole of the dividing cell receives either a paternal or
maternal longitudinally double chromosome of each tetrad. This ensures a
change in chromosome number from diploid to monoploid or haploid in the
resultant reorganized daughter nuclei.
The chromosomes may persist for a time in the condensed state, the nucleolus
and nuclear membrane may be reconstituted, and cytokinesis may also occur to
produce 2 haploid cells.
Metaphase-II is of very short duration. The chromosomes rearrange in the
equatorial plate. The centromere lies in the equator, while the arms are directed
toward the poles. The centromeres divide and separate into 2 daughter
Daughter chromosomes start migrating toward the opposite poles and the
movement is brought about by the action of spindle fibers.
The chromosomes uncoil after reaching the opposite poles and become less
distinct. The nuclear membrane and nucleolus reappear, resulting in the formation
of 4 daughter nuclei, which are haploid.
This separates each nucleus from the others. The cell wall is formed and 4
haploid cells are produced.