The key difference between Barr body and Davidson body is that Barr body is an inactivated X chromosome in somatic cells of females while Davidson body is a nonspecific appendage in polymorphonuclear leukocytes in females.
Sex chromatins in females have two specific structures as Barr body and Davidson body. Barr bodies are the inactivated X chromosomes present in somatic cells in females while Davidson bodies are the drumstick appendages of the polymorphonuclear leukocytes in females. Barr bodies can be visualized in somatic cells using a buccal smear while Davidson bodies can be visualized in a blood smear.
CONTENTS
1. Overview and Key Difference
2. What is Barr Body
3. What is Davidson Body
4. Similarities Between Barr Body and Davidson Body
5. Side by Side Comparison – Barr Body vs Davidson Body in Tabular Form
6. Summary
What is Barr Body?
Barr body is an inactivated X chromosome seen in female somatic cells. This X inactivation takes place during the expression of the genes of somatic cells of females. In males, Barr bodies are absent. Murray Barr named these inactive X chromosomes in female somatic cells as Barr bodies. Barr body is in the state of heterochromatin, which is a transcriptionally inactive structure, while the other copy – active X chromosome – is in the euchromatin state. Once the Barr body is packaged into heterochromatin, none of the molecules involved in transcription can access the chromosome.
Figure 01: Barr Body
Since all females have two X chromosomes, X inactivation or lyonization is important in order to prevent them from having twice as many X chromosome gene products as males. In short, Barr body production ensures that only the necessary amount of genetic information is expressed in females rather than doubling it. Throughout the cell’s whole life, one X chromosome of all somatic cells remains silenced.
What is Davidson Body?
Davidson body is a solitary nuclear appendage of WBC in females. They are drumstick structures with dense chromatic head. Especially in polymorpho-nuclear leukocytes, drumstick shaped mass of chromatin can be seen attached to one end of the nuclear lobe. Structurally, leukocyte Davidson bodies are stalked and rounded chromatin appendages which are 1.5 microns in diameter. They project from the neutrophilic nuclei.
Davidson bodies can be used in sex determination in forensic medicine. A blood smear should be taken from the patient and stained with Leishman’s stain. This is a very easy and reliable method that takes very less time. Moreover, it is a cost-effective method. In fact, these Davidson bodies in blood smear are highly specific. Hence, it is highly used in sex determination studies.
What are the Similarities Between Barr Body and Davidson Body?
- Barr body and Davidson body are found in females.
- They are two types of sex chromatins.
- Both Barr bodies and Davidson bodies are helpful in the identification of an individual.
- Davidson bodies in blood smear and Barr bodies in buccal smear are used for sex determination.
What is the Difference Between Barr Body and Davidson Body?
Barr bodies are condensed and inactivated X chromosomes of somatic cells. Davidson bodies are nonspecific drumstick appendages in neutrophil nuclear lobes. So, this is the key difference between Barr body and Davidson body. Generally, Barr bodies are identified in buccal smear while Davidson bodies are identified in a blood smear.
The below infographic summarizes the difference between Barr body and Davidson body.
Summary – Barr Body vs Davidson Body
Barr body and Davidson body are two types of sex chromatins in females. Barr bodies are present in somatic cells, while Davidson bodies are present in leukocytes. Barr bodies are condensed inactivated X chromosomes in somatic cells. Davidson bodies are drumstick appendages of polymorphonuclear leukocytes. Thus, this is the key difference between Barr body and Davidson body. Both types of structures are seen only in females. Hence they can be used to determination of sex.
Reference:
1. Harikrishnan, Prasad, et al. “Comparison_of_Davidson_Bodies_with_Barr_Bodies.” International Journal of Current Research, May 2018, Available here.
2. R Amirthaa Priyadharscini, TR Sabarinath. “Barr Bodies In Sex Determination”. Pubmed Central (PMC), 2020, Available here.
Image Courtesy:
1. “BarrBodyBMC Biology2-21-Fig1” By Stanley M Gartler, Kartik R Varadarajan, Ping Luo, Theresa K Canfield, Jeff Traynor, Uta Francke and R Scott Hansen – BMC Biology 2004, 2:21 doi:10.1186/1741-7007-2-21 (CC BY 2.0) via Commons Wikimedia