Barr Body: Difference between revisions
No edit summary |
No edit summary |
||
| Line 1: | Line 1: | ||
A '''Barr Body '''is an inactivated | A '''Barr Body '''is an inactivated, condensed X [[Chromosome|chromosome]] found in female cells. | ||
Since females | Since females posses two X chromosomes and males have one X chromosome and a [[Y chromosome|Y chromosomes]], Barr bodies are essential to regulate the amount of X-linked gene product being transcribed. To ensure that X-linked gene product doses are kept similar between males and females, one of the [[X chromosome|X chromosomes]] in a female becomes very condensed - the Barr body. This results in the genetic information on the chromosome being inaccessible to proteins that cause [[Gene|gene]] transcription. This is called [[Dosage Compensation Mechanism|dosage compensation]]. | ||
Inactivation of the X chromosome is random and occurs at an early point of development. | Inactivation of the X chromosome is random and occurs at an early point of development. | ||
| Line 10: | Line 10: | ||
*In a normal male with the genotype 46XY, the number of Barr bodies would be 0. | *In a normal male with the genotype 46XY, the number of Barr bodies would be 0. | ||
However in a male with [[Klinefelter syndrome|Klinefelter's syndrome | However in a male with [[Klinefelter syndrome|Klinefelter's syndrome]] (where the genotype is 47XXY), the number of Barr bodies would also be 1<ref>Page 262, Hartl D.L and Ruvolo M (2012) Genetics, Analysis of Genes and Genomes, 8th edition, USA: Jones and Bartlett</ref><ref>Alberts, B. Johnnson, A. Lewis, J. Raff, M. Roberts, K and Walter, P. (2008) Molecular Biology of The Cell 5th Edition, New York:Garland Science. (page 473)</ref>.<br> | ||
=== Reference === | === Reference === | ||
<references /><br> | <references /><br> | ||
Revision as of 20:21, 12 November 2012
A Barr Body is an inactivated, condensed X chromosome found in female cells.
Since females posses two X chromosomes and males have one X chromosome and a Y chromosomes, Barr bodies are essential to regulate the amount of X-linked gene product being transcribed. To ensure that X-linked gene product doses are kept similar between males and females, one of the X chromosomes in a female becomes very condensed - the Barr body. This results in the genetic information on the chromosome being inaccessible to proteins that cause gene transcription. This is called dosage compensation.
Inactivation of the X chromosome is random and occurs at an early point of development.
The number of Barr bodies in a cell is one less than the number of X chromosomes. For example:
- In a normal female with the genotype 46XX , the number of Barr bodies would be 1.
- In a normal male with the genotype 46XY, the number of Barr bodies would be 0.
However in a male with Klinefelter's syndrome (where the genotype is 47XXY), the number of Barr bodies would also be 1[1][2].