Buccal Epithelial Smear and Barr Body

The study of the Barr body from the (female) smear of Buccal epithelial cells.

Materials

• Buccal epithelial cells
• Giemsa stain
• Carnoy’s fixative
• Slides
• Cover slip
• Microscope, etc.

Procedure

1. Gently rub the inside of the cheek with a flat rounded piece of wood and transfer the scraping over a clean glass slide.
2. Then, made a thin film of cells on the slide and keep them for air-drying.
3. Air-dried smear was kept in Carnoy’s fixative for 30–35 minutes.
4. Then, the Giemsa stain was poured and allowed to stand for 20–25 minutes.
5. After staining, the slide was washed with distilled water to remove the excess stain.
6. Finally, the slide was kept for air-drying and then observed under the microscope.

Observations
We found that very lightly stained cells are scattered here and there in the smear. In the cells, violet-Barr bodies are observed inside a pink nucleus. A Barr body is nothing but an inactivated (heterochromatinized) X chromosome. It was first observed by Murray Barr in 1949. It is found only in female cells, because in those 1 X chromosome is enough for metabolic activity. It is absent in male somatic cells, because there only 1 X chromosome is present, which is in an active state.

Precautions
The smear or film should be uniform and thin over the glass slide so that the cells will not overlap each other.