# Single X chromosome (Turner syndrome) \[duplicate -- locked\]

**URL:** https://boards.straightdope.com/t/single-x-chromosome-turner-syndrome-duplicate-locked/513919
**Category:** Factual Questions
**Created:** [October 15, 2009, 5:09pm UTC](https://boards.straightdope.com/t/single-x-chromosome-turner-syndrome-duplicate-locked/513919 "2009-10-15T17:09:01Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)
#### Post date: [October 15, 2009, 5:09pm UTC](https://boards.straightdope.com/t/single-x-chromosome-turner-syndrome-duplicate-locked/513919/1 "2009-10-15T17:09:01Z")

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I am just asking this for curiosity. Normally females have two X chromosomes, but in every cell, only one is active and the other is curled up into something called a “Barr body”. So a woman is a mosaic, with adjacent cells perhaps having made the opposite choice of which X to inactivate.

There must, however, be more to it than that. For you wouldn’t expect any abnormality to result if a woman had only one X chromosome, only she wouldn’t be a mosaic. Every normal male has only one X and no abnormality results. But that is wrong. A single X female is definitely not normal, see [Turner syndrome - Wikipedia](http://en.wikipedia.org/wiki/Turner_syndrome) for details. Can anyone explain how this differs from what happens in normal females?