Buccal smear-Identification of Barr Body
Barr body, the inactive X chromosome in female cells, plays a crucial role in dosage compensation. Learn about its discovery, location, frequency, and reasons for testing. Explore how this structure aids in sex determination and understanding gender identity.
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TIU - Faculty of Applied Science Medical Analysis Department Buccal smear-Identification of Barr Body https://tiu.edu.iq/ 2021 - 2022 Lecturer name: Dr. Jibril H. Yusuf Lecturer name: Dr. Jibril H. Yusuf Assistant : CHNAR Assistant : CHNAR
Introduction What is Barr body: A Barr body is the inactive X chromosome in a female somatic cell. This is known as sex chromatin or Barr body after the name of its discoverer Murray Barr in 1940. Inactivated condensed X chromosome found in female cells X chromosome Inactivation is random and occurs at an early point of development
Need for Barr body: To regulate the amount of X-linked gene product, that is dosage compensation. Dosage Compensation: In sex determination mechanism, the female have XX chromosomes while the male have just one. To compensate this, one of the X chromosome is inactive in females. X chromosome Inactivation is random and occurs early in embryonic life and remained fixed.
Where is Barr body found? Found in the nucleus of somatic cells in female. It can be seen clearly during interphase Commonly situated at the periphery of the nucleus In nerve cells it may be near the nucleolus or near the nuclear envelope. In buccal epithelial cells, it is general attached to the nuclear envelope. In neutrophils, it may appear as a small rod called drumstick.
Frequency of Occurrences: In nervous tissue the frequency may be 85% Chorionic epithelium it may be as high as 96% In oral smears it may vary between 20 to 50%
Reasons for Barr body test: To identify person s gender and to establish sexual identity in newborns and adults. As a screening test for ambiguous genitalia Delayed onset of puberty Crime scene detection.
Aim: o To identify the presence of Barr body in the female Buccal cavity. Principle: o Buccal epithelial cells especially have Barr body structure, which are considered to play a major role for sex determination. o This small round Barr body is located either in the border of nuclear membrane or sometimes inside of nucleus. o This Barr body may be single or more in number in some cases. o These structures are present only in the female sex.
Materials required: Slide o Coverslip o Wooden spoon o Methylene blue stain o Glycerin o Compound microscope o Epithelial cells (sample) o
Methodology: 1. Wash your mouth with sterile water to prepare mucous. 2. Take a sterilized slide and scrap epithelial cells superficially from the inner side skin of the mouth. 3. Keep the sample on the center of the pre sterilized glass slides and dry it for few minutes (5-10 mins). 4. Then add few drops of methylene blue stain and spread it to entire smear by tilting the slide. 5. Wash off the excess stain gently under running tap water
6. Dry the slide in air for 10 mins. 7. Eventually, blot the water using tissue paper. 8. Place a drop of glycerin on the smear and cover it with slip. 9. The smear is now ready for microscopic observation. 10. Observe under microscope (high power) record and discuss your observation.
