To examine the presence or absence of Barr body in the given sample

 Practical Notebook Biology Standard XII

Biology 

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Practical Notebook
Standard XII

Class-12th

science

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12. To examine the presence or absence of Barr body in the given sample.  

Alm:

 To observe Barr bodies in squamous epithelial cells obtained from the inner lining of the check (Buccal smear).  Requirements: Cotton buds, slide saline solution, 70% alcohol, Giemsa / Methylene blue stain compound microscope, etc 

Procedure: 

1. Clean the mouth by rinsing and gargling with water, several times.  
2. Take a sterile cotton bud and in normal saline solution 
3.  Rub it on the inner lining of the cheek several times.  
4. Smear the bud on a clean slide and allow it to dry.  
5. Place the slide in a Petri dish.  Layer it with a fixative (70% alcohol).  
6.  Allow it to stand for a few minutes.  
7.  Drain off the extra fixative.  
8.  Stain the smear with Giemsa / Methylene Blue and wait for 10 minutes.  
9.  With the help of a dropper gently wash off the excess stain with water.  
10. 10. Place a coverslip and observe first under low power and then under high power of the microscope.  

Observation: 

1. Barr body is seen attached on the inner side of the nuclear membrane of the cell.  
2. A Barr body (named after its discoverer Dr. Murray Barr is the condensed, inactive X process called lyonization. Chromosome found in the female somatic cell. The chromatin body is made inactive by a cell of a normal male. 
3.  The number of Barr bodies seen in a cell is one less than the number of chromosomes in the somatic cell. Hence only one Barr body is seen in the cell of a normal female and never in the Result: X number of Barr body is seen in the slide  

Figure: Draw the diagram of the Barr body and the cell as seen under the microscope