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  Section: Biotechnology Methods » Cell Biology and Genetics
 
 
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Meiosis in Flower Buds of Allium Cepa-Acetocarmine Stain

 
     
 
Content
Cell Biology and Genetics
  Cell Cycles
  Meiosis in Flower Buds of Allium Cepa-Acetocarmine Stain
  Meiosis in Grasshopper Testis (Poecilocerus Pictus)
  Mitosis in Onion Root Tip (Allium Cepa)
  Differential Staining of Blood
  Buccal Epithelial Smear and Barr Body
  Vital Staining of DNA and RNA in Paramecium
  Induction of Polyploidy
  Mounting of Genitalia in Drosophila Melanogaster
  Mounting of Genitalia in the Silk Moth Bombyx Mori
  Mounting of the Sex Comb in Drosophila Melanogaster
  Mounting of the Mouth Parts of the Mosquito
  Normal Human Karyotyping
  Karyotyping
  Black and White Film Development and Printing for Karyotype Analysis
  Study of Drumsticks in the Neutrophils of Females
  Study of the Malaria Parasite
  Vital Staining of DNA and RNA in Paramecium
  Sex-Linked Inheritance in Drosophila Melanogaster
  Preparation of Somatic Chromosomes from Rat Bone Marrow
  Chromosomal Aberrations
  Study of Phenocopy
  Study of Mendelian Traits
  Estimation of Number of Erythrocytes [RBC] in Human Blood
  Estimation of Number of Leucocytes (WBC) in Human Blood
  Culturing Techniques and Handling of Flies
  Life Cycle of the Mosquito (Culex Pipiens)
  Life Cycle of the Silkworm (Bombyx Mori)
  Vital Staining of Earthworm Ovary
  Culturing and Observation of Paramecium
  Culturing and Staining of E.coli (Gram’s Staining)
  Breeding Experiments in Drosophila Melanogaster
  Preparation of Salivary Gland Chromosomes
  Observation of Mutants in Drosophila Melanogaster
  ABO Blood Grouping and Rh Factor in Humans
  Determination of Blood Group and Rh Factor
  Demonstration of the Law of Independent Assortment
  Demonstration of Law of Segregation

Materials
  • Onion flower
  • Acetocarmine stain
  • Glass slides
  • Cover slips
  • blotting paper
Procedure
  1. Select appropriate flower buds of different size from the inflorescence.
  2. Fix them in Carnoy’s fluid, which is used as fixative.
  3. Take a preserved flower bud and place it on a glass slide.
  4. Separate the anthers and discard the other parts of the bud.
  5. Put 1 or 2 drops of acetocarmine stain and squash the anthers.
  6. Leave the material in the stain for 5 minutes.
  7. Place a cover slip over them and tap it gently with a needle or pencil.
  8. Warm it slightly over the flame of a spirit lamp.
  9. Put a piece of blotting paper on the cover slip and apply uniform pressure
    with your thumb.
  10. Observe the slide under the microscope for different meiotic stages.
Interphase
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.

Prophase-I
In the first meiotic division, production in the chromosome number occurs without separation of chromatids. Prophase is the longest phase and has 5 stages.

Leptotene
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.

Zygotene

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.

Pachytene
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.

Diplotene
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.

Diakinesis

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 underway.

Metaphase-I

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.

Anaphase-I

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.

Telophase-I
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

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 chromosomes.

Anaphase-II

Daughter chromosomes start migrating toward the opposite poles and the movement is brought about by the action of spindle fibers.

Telophase-II
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.

Cytokinesis
This separates each nucleus from the others. The cell wall is formed and 4 haploid cells are produced.

 
     
 
 
     




     
 
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