Brief Discussion of Buccal Smear for Barr Bodies (Sex Chromatin)

A buccal smear for Barr bodies is a simple, non-invasive test used to demonstrate sex chromatin, which represents the inactive X chromosome present in somatic cells. The sample is obtained by gently scraping the buccal (oral) mucosa and preparing a smear on a glass slide.

On microscopic examination after appropriate staining, Barr bodies appear as small, dark-staining dots at the periphery of the nucleus. They are typically present in females (XX) and absent in normal males (XY). This test is useful in sex determination and in the evaluation of sex chromosome abnormalities, such as Turner syndrome (XO) and Klinefelter syndrome (XXY).

Although largely replaced by modern genetic techniques, buccal smear examination remains a quick, inexpensive screening method for assessing chromosomal sex.