page_title: X-inactivation
hierarchical_section_title: X-inactivation
caption_attribution_description: English: Nucleus of a female amniotic fluid cell. Top: Both X-chromosome territories are detected by FISH. Shown is a single optical section made with a confocal microscope. Bottom: Same nucleus stained with Dapi and recorded with a CCD camera. The Barr body is indicated by the arrow, it identifies the inactive X (Xi). Preparation of specimen as described in: R Eils, S Dietzel, E Bertin, E Schrock, MR Speicher, T Ried, M Robert-Nicoud, C Cremer and T Cremer (1996): Three-dimensional reconstruction of painted human interphase chromosomes: active and inactive X chromosome territories have similar volumes but differ in shape and surface structure. Journal of Cell Biology, Vol 135, 1427-1440. PMID:8978813. Website. Deutsch: Kern einer weiblichen menschlichen Zelle aus Amnionflüssigkeit. Oben: Darstellung beider X-Chromosomen durch Fluoreszenz-in-situ-Hybridisierung. Gezeigt ist ein einzelner optischer Schnitt, der mit einem konfokalen Laserscanningmikroskop erzeugt wurde. Unten: der gleiche Kern mit Dapi-Färbung, aufgenommen mit einer CCD-Kamera. Das Barr-Körperchen ist hier gut zu erkennen (Pfeil) und identifiziert das inaktive X-Chromosom (Xi). Präparation wie in: R Eils, S Dietzel, E Bertin, E Schrock, MR Speicher, T Ried, M Robert-Nicoud, C Cremer and T Cremer (1996): Three-dimensional reconstruction of painted human interphase chromosomes: active and inactive X chromosome territories have similar volumes but differ in shape and surface structure. Journal of Cell Biology, Vol 135, 1427-1440. PMID:8978813. Website. 한국어: 여성 양수에 떠있는 세포의 핵. 위: FISH(Fluorescence in situ hybridization)법을 통해 두개의 X염색체를 볼 수 있다. 이 사진은 공초점 레이저 현미경에 의해 찍혔다. 아래&#160;: 같은 핵을 다피 염색(DAPI)법을통해 염색하고, CCD 카메라로 찍은 사진이다. 화살표가 가리키는 것이 바소체이고, Xi로 표시된 것이 불활성화된 X염색체이다(inactive X (Xi). 사진에 관한 내용: R Eils, S Dietzel, E Bertin, E Schrock, MR Speicher, T Ried, M Robert-Nicoud, C Cremer and T Cremer (1996): Three-dimensional reconstruction of painted human interphase chromosomes: active and inactive X chromosome territories have similar volumes but differ in shape and surface structure. Journal of Cell Biology, Vol 135, 1427-1440. PMID:8978813. Website.
context_page_description: X-inactivation is a process by which one of the copies of the X chromosome is inactivated in therian female mammals. The inactive X chromosome is silenced by it being packaged into a transcriptionally inactive structure called heterochromatin. As nearly all female mammals have two X chromosomes, X-inactivation prevents them from having twice as many X chromosome gene products as males, who only possess a single copy of the X chromosome.
  The choice of which X chromosome will be inactivated is random in placental mammals such as humans, but once an X chromosome is inactivated it will remain inactive throughout the lifetime of the cell and its descendants in the organism. Unlike the random X-inactivation in placental mammals, inactivation in marsupials applies exclusively to the paternally-derived X chromosome.
context_section_description: X-inactivation (also called lyonization, after English geneticist Mary Lyon) is a process by which one of the copies of the X chromosome is inactivated in therian female mammals. The inactive X chromosome is silenced by it being packaged into a transcriptionally inactive structure called heterochromatin. As nearly all female mammals have two X chromosomes, X-inactivation prevents them from having twice as many X chromosome gene products as males, who only possess a single copy of the X chromosome (see dosage compensation).
  The choice of which X chromosome will be inactivated is random in placental mammals such as humans, but once an X chromosome is inactivated it will remain inactive throughout the lifetime of the cell and its descendants in the organism. Unlike the random X-inactivation in placental mammals, inactivation in marsupials applies exclusively to the paternally-derived X chromosome.
caption: Nucleus of a female cell. Top: Both X-chromosomes are detected, by FISH. Bottom: The same nucleus stained with a DNA stain (DAPI). The Barr body is indicated by the arrow, it identifies the inactive X (Xi).
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