# Mirror twins?

**URL:** <https://boards.straightdope.com/t/mirror-twins/171187>\
**Category:** Factual Questions\
**Created:** [April 25, 2003, 8:31pm UTC](https://boards.straightdope.com/t/mirror-twins/171187 "2003-04-25T20:31:32Z")\
**Posts on this page:** 3\
**Page:** 2

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**Author:** ![The\_Tim](https://avatars.discourse-cdn.com/v4/letter/t/ec9cab/32.png) [@The\_Tim](https://boards.straightdope.com/u/The_Tim)\
**Post date:** [April 27, 2003, 7:17am UTC](https://boards.straightdope.com/t/mirror-twins/171187/21 "2003-04-27T07:17:22Z")

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Ah thanks **nevermore** I knew that the cat thing had to do with the nifty fur patterns but it was tossed out by the behavioral genetics prof to help illustrate the point before moving on.

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**Author:** ![Jodocus](https://avatars.discourse-cdn.com/v4/letter/j/f04885/32.png) [@Jodocus](https://boards.straightdope.com/u/Jodocus)\
**Post date:** [April 27, 2003, 7:23am UTC](https://boards.straightdope.com/t/mirror-twins/171187/22 "2003-04-27T07:23:56Z")

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Why are genetic mosaics only limited to females? I mean only one set of chromosomes in males are XY the rest as I understand it are XX? So these XX chromosomes should be able to switch between inactive and active genes as well? Right?

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**Author:** ![KontagiousKaren](https://avatars.discourse-cdn.com/v4/letter/k/ee59a6/32.png) [@KontagiousKaren](https://boards.straightdope.com/u/KontagiousKaren)\
**Post date:** [April 27, 2003, 7:42pm UTC](https://boards.straightdope.com/t/mirror-twins/171187/23 "2003-04-27T19:42:56Z")

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what book are you reading, Sua?

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