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  Section: Biotechnology Methods » Cell Biology and Genetics
 
 
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Meiosis in Grasshopper Testis (Poecilocerus Pictus)

 
     
 
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

The testes of the grasshopper are removed and fixed in Carnoy’s fluid. After 2–14 hours, the testes are transferred to 10% alcohol and stored.

Squash Preparation

  1. 1 or 2 lobes of the testes are removed.
  2. The testes are placed on a glass slide.
  3. Apply 1 to 2 drops of acetocarmine stain.
  4. With a sharp blade, the teste lobes are cut into minute pieces and kept for
    10 minutes.
  5. The slide is then gently covered with a coverslip, taking care so that air
    bubbles are not formed.
  6. Warm the slide gently and place it between 2 folds of filter paper.
  7. Press the material with the tip of the finger and remove the excess stain,
    which comes out on the sides of the coverslip.
  8. The slide is observed under the microscope.

Interphase
This phase is usually present in animal cells. The cells in this stage are physiologically active. No DNA replication takes place.

Prophase-I
  1. Leptotene. The chromosomes are long, standard, and uncoiled. They are densely formed on 1 side of the cell. Only 1 sex chromosome occurs in the males, which normally replicates later and hence appears as a dark skin body.
  2. Zygotene. Homologous chromosomes pair by a process called synapsis. Pairing starts from many points on the chromosome. The chromosomes are called bivalents. Bivalents become shortened and thickened by coiling and condensation. Synapsis of a chromosome is cemented by a complex called synaptonemal complex, which facilitates crossing over.
  3. Pachytene. Crossing over takes place between nonsister chromatids. Crossing over is accompanied by the chiasmata formation.
  4. Diplotene. Condensation of chromatid material is greater. Each chromosome can be distinguished separately.
  5. Diakinesis. Homologous chromosomes begin to coil and become shorter and thicker. Chromosomes are fully contracted and deeply stained. The ‘X’ chromosome is rod-shaped, univalent, and easily distinguishable from the rest of the chromosomes.

Metaphase-II
The chromosomes get oriented in the equatorial region of the spindle and their centromeres are attached to the chromosomal fibers. Each chromosome is easily seen. Maximum concentration occurs at this stage.

Anaphase-II
The spindle fibers contract and the homologous chromosomes separate and move toward the opposite poles. Each chromosome consists of 2 chromatids attached to 1 centromere.

Telophase-I
The separation of homologous chromosomes is completed. They reach the opposite poles. Two distinct daughter nuclei are formed. The daughter nuclei formed contain only half the number of chromosomes present in the parent cell. Cytokinesis may occur after the completion of telophase.

Prophase-II

The chromosomes with 2 chromatids become short and thick. This is the stage of the second meiotic division. The nuclear membrane and the nucleolus are absent. The spindle is formed and the chromosomes are arranged on the equator.

Anaphase-II

The spindle is formed. The centromeres of the daughter chromosomes are attached to the spindle fibers. The 2 groups of the daughter chromosomes in each cell have started moving apart toward the opposite poles of the spindle.

Telophase-II
The 2 groups of daughter chromosomes in each haploid cell have reached the 2 poles of the spindle. The 2 haploid daughter cells formed as a result of first meiotic division divide again by the second meiotic division. Four haploid cells are formed from a single diploid cell.

 
     
 
 
     




     
 
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