Barr body Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Barr body and links to relevant pages within the course.
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The segmented neutrophil is the end stage of maturation in the myeloid lineage. The cell is similar in size to the band neutrophil and has a well granulated cytoplasm with a deeply condensed, knotted and clumped chromatin pattern. The chromatin pinches into several segments, usually separated by visible filaments. In some segmented neutrophils, this filament is inferred by the folding and shape of the nucleus.The top image on the right shows the classic morphology of a segmented neutrophil. The nucleus of a normal segmented neutrophil has two to five lobes, connected by thin filaments. Six or more lobes is an indication of abnormal development, usually related to B12 or folate deficiency.The bottom image shows the progression from band neutrophil (red arrows) to early segmented neutrophil (blue arrow) and finally to fully-mature segmented neutrophil (green arrow). Take a close look at the cell closest to the promyelocyte. You can see a drumstick-like projection arising from the end terminal segment. This can be seen in smears on female patients and is a Barr body or inactivated X-chromosome.
A Barr body (see image) appears as a small drumstick-like projection on one of the lobes of some neutrophils in females. Barr bodies are attached to the nuclear lobe by a single narrow stalk, which distinguishes them from other thicker projections, sometimes referred to as "clubs." Since Barr bodies are the morphological expression of the inactivated X chromosome, Barr bodies (one per neutrophil) can be seen in up to 3% of the neutrophils on a female's peripheral blood slide. In rare chromosome disorders in which three or more X chromosomes are present, two to three Barr bodies per neutrophil can be seen. Barr bodies must also be distinguished from hair-like projections sometimes seen in the band form, following irradiation or in patients with a malignant tumor that has metastasized. Recognition of a Barr body in a neutrophil is important in order to avoid reporting it as abnormal (unless two or more per neutrophil are seen). The Barr body is considered nonpathological unless associated with rare chromosome disorders.
|Barr Bodies may be Normal or Pathological|
The Barr body is considered nonpathological unless associated with the rare chromosome disorders, in which case it would be pathological.
A Barr body is indicated by the arrow in this image.
|Which of the following best describes a Barr body?||View Page|
|Barr Body (cont.)|
The arrow in this image points to another example of a Barr body.
|The nuclear appendage at the tip of the arrow is a normal finding in females but not in males.||View Page|
|The small club-shaped, "drumstick" nuclear appendage attached to one lobe of a neutrophil (marked by the blue arrow in the image) may be found in:||View Page|