Barr Bodies detection and Drumstick
Sample for Barr Bodies
- Scrapings from buccal mucosa or the vaginal wall in some women.
- The buccal mucosa is scrapped and smears the slide. It is fixed immediately. Make a monolayer of the cells.
- While the Drumstick is done on the white cells (WBC) to see the presence of the drumstick.
- The more specific method is a nucleic acid probe, which is more sensitive than Barr bodies.
Indications for Barr Bodies
- This is an easy and cheapest test.
- This screening test is for ambiguous genitalia (where the sex characters are unclear).
- It may be done for the delayed onset of puberty.
- This test may be done for Turner and Klinefelter syndromes.
Precautions for barr body sample
- Don’t take the sample during the first week of the life of newborns.
- Don’t take samples during the adrenocorticosteroids or estrogen therapy. This will lead to a decrease in the number of Barr bodies.
- Inadequate preparation may obscure the chromosome Barr bodies.
- 40% to 60% of the cells show identifiable Barr bodies.
Definition of Barr Bodies:
- Barr bodies or nuclear sexing is where buccal or vaginal smears are stained with cresyl violet and examined microscopically.
- A dense barr body on the nuclear membrane represents one of the X-chromosomes, occurring in 30% to 60% of females.
- Barr bodies are stainable structures.
- Barr bodies are present in the nucleus, and there are stainable sex chromosomes. Barr body that appears for each X-chromosome.
- So XX females will show one bar body, while the male has XY chromosome will show no barr body.
- So if there are XXY, it will show two barr bodies.
History of the Barr Bodies:
- The barr bodies are named after the discoverer Murray Barr and Bertram in late 1940.
- This is also called sex chromatin.
- 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 of Barr Bodies Formation:
- This inactivation occurs very early in embryonic development, approximately 7 to 14 days after fertilization.
- One of the chromosomes, XX, one of those is inactivated.
- Sometimes one of the inactivated X chromosomes is donated by the father.
- In other is contributed by the mother.
- This cell with an inactivated X chromosome gives the descendant the same structure.
- This helps determine sex where the infants’ physical features are unclear.
- Denver classification, toat chromosomes are 46 in number:
- 22 pairs.
- One pair shows XX, indicating female.
- Other pairs may show XY, indicating male.
- Denver classification, toat chromosomes are 46 in number:
- So the female XX chromosome has one bar body and is considered chromatin positive.
- While male has XY, so no barr body and considered chromatin negative.
Procedure for Barr bodies:
- Take epithelial cells from the buccal mucosa or vaginal smear.
- Make a monolayer cell slide.
- Fix these cells by the fixative.
- Stain with cresyl violet.
- Examine under the microscope.
- There is a dense body (Barr body) on the nuclear membrane; it represents one of the X-chromosomes.
- This will be seen in 30% to 60% of the female somatic cells (other than the reproductive cells).
Drumstick in the neutrophils:
- The drumstick is the drum-shaped nuclear appendage seen in 2% to 3% of the neutrophils in females, indicating 2 X chromosomes. This can be confirmed by karyotyping.
- It is not found in males.
- There is a lower incidence of the drum-stick in Klinefelter syndrome (XXY) as opposed to the extra barr body.
- Double drum-stick are exceedingly rare and have no diagnostic value.
Normal Barr Body
- Male = No barr bodies are seen.
- Female = Barr’s body is positive.
|Number of Barr bodies||Possible sex character|
- Drumstick positive in females (2% to 3% of polys) indicates the presence of two X chromosomes.
- Drumstick negative in males.
- If <10% of cells contain the Barr Bodies in patients with female sex organs, chromosomal karyotyping is recommended to find any abnormality.
Interpretations of Barr Body (Drumstick)
- This barr body test is advised to screen ambiguous or doubtful sex characters.
- Female (XO) will have no barr body.
- This is a chromosomal sexual abnormality in females.
- These patients have one chromosome deletion showing only 45 chromosomes instead of 46.
- There is a deficiency of secondary sexual features and small genitalia.
- There may be a webbing of the neck, coarctation of the aorta, and short fingers.
- They don’t mensurate and usually lack ovaries.
- Buccal smear for Barr bodies will be negative.
- If Barr’s body is positive, then advise chromosomal karyotyping because sometimes these patients have 50% positive and 50% negative cells for Barr’s bodies.
- A male with (XXXY) will have a barr body.
- The person looks like a male, but the chromosomes show XXY or XXXY.
- Ther external genitalia is normal except for small testes.
- There are decreased body hairs, and may be gynaecomastia.
- There is a mental deficiency, but they may have normal intelligence.
- Mostly these patients are sterile.
- The biopsy will confirm the diagnosis, showing atrophic semniferous tubules.
- Chromosomal karyotyping is the method of choice.
- Females with XXX chromosomes 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.
Questions and answers:
Question 1: What precautions are needed for Barr bodies detection.
Don't advise in the first week of the newborn and patients on corticosteroids therapy
Question 2: What is the difference between Barr body and drumstick?
Barr body is the condensation at the periphery of the nucleus, while drumstick is drumstick-like projections coming out from the nucleus of WBCs.