Barr Body detection (sex chromatin body)
- Scrapings from buccal mucosa, or in some women from the vaginal wall.
- The buccal mucosa is scrapped and smear the slide.
- While the Drumstick is done on the white cells (WBC) to see the presence of the drumstick.
- This is an easy and cheapest test.
- This is a screening test for the ambiguous genitalia (where the sex characters are not clear).
- It may be done for the delayed onset of puberty.
- This test may be done for Turner syndrome and Klinefelter syndrome.
- The barr bodies are named after the discoverer Murray Barr and Bertram in late 1940.
- This is also called sex chromatin.
- The inactivated X chromosome is observable in many interphase cells as highly condensed intranuclear chromatin bodies are Barr bodies.
- The barr body is the inactive X chromosome in the female somatic cells.
- This is basically a compact structure of the chromatin in the nuclei in the female.
- Barr body is the condensed chromatin, dark staining spot at the periphery of the nucleus of each somatic cell in the human body.
- Mechanism: This inactivation occurs very early in embryonic development, approximately 7 to 14 days after fertilization.
- One of the chromosome XX, one of those is inactivated.
- Sometimes one of the inactivated X chromosomes is donated from the father.
- In other is contributed by the mother.
- This cell with an inactivated X chromosome gives the descendant with the same structure.
- This helps in the determination of sex where the physical features are not clear in the infants.
- So the female XX chromosome has one bar body and considered chromatin positive.
- While male has XY, so no barr body and considered chromatin negative.
- Male = No barr bodies are seen.
- Female = Barr body is positive.
- This barr body test is advised for the screening of ambiguous or doubtful sex characters.
- Turner’s syndrome female (XO) will have no barr body.
- Male with Klinefelter syndrome (XXY) will have a barr body.
- Female with XXX chromosome will have two barr bodies.
- The female cell with four X chromosomes has three barr bodies.
If needed the result should be confirmed by chromosomal karyotyping.