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Related to Lyon hypothesis: Barr body
Lyon hypothesis[′lī·ən hī‚päth·ə·səs]
The concept that mammalian females are X-chromosome mosaics as a result of the random inactivation of one X chromosome in some embryonic cells and their descendant and of the other X chromosome in the rest.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.