Molecular Test Detection

Test : Sex chromatin test


Indications : The test is a simple method to identifying a person’s gender and establish sexual identity in newborns and in adults. Earlier the method was popularly employed in competitive sports to identify males masquerading as females.

The mouth has to be rinsed and washed before the test. A spatula is used to gently scrape the inside of the person’s cheek. This can be done by a health care provider or by self. A smear of this buccal sample is made on a slide, stained and observed under the microscope.

Physiology : A buccal smear is a painless test to detect Barr bodies in a sample of cells from inside the mouth (cheek).

The test was widely employed earlier to identify men pretending to be women, which gave them a greater advantage in women’s sports. There have been several such cases of masquerading and fraud that outraged the public across the world.

Most of the individuals involved had ambiguous genitalia which occurred due to psudohermaphroditism. As physical examination was widely unacceptable, sex chromatin or the buccal smear technique was introduced in 1960 for gender identification.

Interpretation : A person who is a biological female (46,XX) has a single Barr body or sex chromatin while there is an absence of it in biological males (46,XY). In short the number of sex chromatin mass or Barr body will be one less than the number of X chromosomes that a person carries. However, this test is not widely employed due to its low sensitivity and large frequencies of errors.

Now the polymerase chain reaction is carried out to detect the presence of the SRY gene which is supposed to be the true determinant for maleness.

Sample : Presence of >4% cells in which clear sex chromatin bodies are found

Related Tests : Scrape from buccal mucosa

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