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  Section: Biotechnology Methods » Cell Biology and Genetics
 
 
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Induction of Polyploidy

 
     
 
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

Cytological Techniques
This involves various steps like choice of treatment, pretreatment, fixation, staining and squashing, and material choice. Healthy root tips are taken, which are excised late in the morning. After thorough washing, these root tips are handled directly, or can be subjected to pretreatment.

Pretreatment

Treat the materials for cytological studies with physical and chemical agents like colchicines, 8-hydroxy quinoline, para dichloro benzene, etc. Pretreatment can be done before or after fixation of the materials.

Objectives of Pretreatment
  • Removal of extra deposits on the cell walls, especially waxy or oily deposits. Otherwise, these extra deposits get in the way of fixation. Chloroform is recommended for the dissolution of the waxy substance.
  • To clear the cytoplasm and make it transparent. This is done by using 1N HCl. Certain enzymes, like cellulose and pectinases, are also used for dissolving certain substances.
  • To soften the tissues—it involves the dissolution of the middle lamella that connects the adjacent cells. In plants, 1N HCl is used.
  • To increase the frequency of nuclear division. This is done through colchicine, which induces nuclear division. It also destroys spindles.
  • To bring about the differential condensation of chromosome at metaphase. This refers to the coiling of the chromosomes.
  • Demonstration of the heterochromatin in the chromosome for this special treatment is needed, i.e., low-temperature treatment.

Mitotic Poisons
These are the chemicals that bring about the arrest of the mitotic apparatus in dividing cells and result in scattering of chromosomes. They do not affect the cell in any other way. A very large variety of chemicals are used. The most effective of them are colchicine, gammaxene and their derivatives, 8-hydroxy quinoline and para dichloro benzene.

Colchicine

It is a poisonous alkaloid that occurs in the liliacae plant, colchicual autumnase (Autumn lilly). It is a small plant with small corn, native to Europe and the UK. Alkaloid is positive in underground corn and seed. Seeds are said to be the chief source of colchicine.

Action of Colchicine

It is believed that the organization of the mitotic apparatus depends upon balance between the elements of cytoplasm and the mitotic apparatus. Any chemical that disturbs this delicate balance will prevent the formation of the mitotic apparatus, and colchicine is said to have this property.

Preparation of Colchicine Solution

In the case of onion root tips the strength of the prepared solution is 0.05% (i.e., 100 mL of H2O, 0.5 mg of colchicine). This treatment to the root tips at room temperature varies from 1 to 1½ hours.
 
     
 
 
     




     
 
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