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  Section: Biotechnology Methods » Cell Biology and Genetics
 
 
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Preparation of Salivary Gland Chromosomes

 
     
 
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

To prepare salivary gland chromosomes in Drosophila melanogaster.

Materials
  • Stereo zoom/Dissecting microscope
  • Third instar larva
  • 1N HCl
  • Physiological saline (0.7% NaCl)
  • Lacto aceto orcein
  • 45% acetic acid
  • Nail polish or wax for sealing
  • Slides and cover slips
Procedure
  1. Dissect the salivary gland of the third instar in physiological saline.
  2. Place it in 1N HCl for 2–3 min.
  3. Transfer it to 2% Lacto Aceto orcein stain for 30 min.
  4. Squash it with freshly prepared 45% acetic acid.
  5. Seal the edges of cover slips with nail polish or wax.
  6. Observe under the microscope for polytene chromosome.
Description
  1. Edouard-Gérard Balbiani, in 1881, observed salivary gland chromosomes in Chironomous larva.
  2. Theophilus Painter discovered the same in Drosophila melanogaster.
  3. The polytene chromosomes are the largest chromosomes available for cytological studies.
  4. These chromosomes are clearly seen in the third instar larva of Drosophila melanogaster.
  5. The salivary gland chromosomes undergo somatic pairing and endoduplication without separation.
  6. This multistranded chromosome contains 1024 chromosomal fibrils.
  7. When stained, chromonema shows bands and interbands.
  8. Along the length, there are bulged regions called Balbiani rings, or puffs,
    which are the sites of genetic action.
  9. Thus, this chromosome has a common chromocenter, with 5 long areas
    radiating outwards.
 
     
 
 
     




     
 
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