Lyon hypothesis

[li´on] the random and fixed inactivation (in the form of sex chromatin) of all X chromosomes in excess of one in mammalian cells at an early stage of embryogenesis, leading to mosaicism for X-linked genes in the female, since the paternal X chromosome is inactivated in some cells and the maternal one in the remainder.

ly·on·i·za·tion

(lī'on-i-zā'shŭn), The normal phenomenon that wherever there are two or more haploid sets of X-linked genes in each cell all but one of the genes are inactivated apparently at random and have no phenotypic expression. Lyonization is usual but not invariable for all loci. Its randomness explains the more variable espressivity of X-linked traits in women than in men. Lyonization occurs in men with the Klinefelter (XXY) karyotype.
See also: gene dosage compensation. Synonym(s): Lyon hypothesis, X inactivation, X-inactivation [M. Lyon]

ly·on·i·za·tion

(lī'on-ī-zā'shŭn) The normal phenomenon whereby wherever there are two or more haploid sets of X-linked genes in each cell, all but one of the genes are inactivated apparently at random and have no phenotypic expression. Its randomness explains the more variable expressivity of X-linked traits in women than in men.
See also: gene dosage compensation
Synonym(s): Lyon hypothesis, X-inactivation. [M. Lyon]

Lyon hypothesis

See X-INACTIVATION.

Lyon hypothesis

see INACTIVE-X HYPOTHESIS.

Lyon,

Mary F., English cytogeneticist, 1925–. Lyon hypothesis - Synonym(s): lyonizationlyonization - the normal phenomenon that wherever there are two or more haploid sets of X-linked genes in each cell, all but one of the genes are inactivated, apparently at random, and have no phenotypic expression. Synonym(s): Lyon hypothesis; X-inactivation

单词	lyon hypothesis
释义	DictionarySeehypothesis Lyon hypothesis Lyon hypothesis [′lī·ən hī‚päth·ə·səs] (genetics) 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. Lyon hypothesis Lyon hypothesis [li´on] the random and fixed inactivation (in the form of sex chromatin) of all X chromosomes in excess of one in mammalian cells at an early stage of embryogenesis, leading to mosaicism for X-linked genes in the female, since the paternal X chromosome is inactivated in some cells and the maternal one in the remainder. ly·on·i·za·tion (lī'on-i-zā'shŭn), The normal phenomenon that wherever there are two or more haploid sets of X-linked genes in each cell all but one of the genes are inactivated apparently at random and have no phenotypic expression. Lyonization is usual but not invariable for all loci. Its randomness explains the more variable espressivity of X-linked traits in women than in men. Lyonization occurs in men with the Klinefelter (XXY) karyotype. See also: gene dosage compensation. Synonym(s): Lyon hypothesis, X inactivation, X-inactivation [M. Lyon] ly·on·i·za·tion (lī'on-ī-zā'shŭn) The normal phenomenon whereby wherever there are two or more haploid sets of X-linked genes in each cell, all but one of the genes are inactivated apparently at random and have no phenotypic expression. Its randomness explains the more variable expressivity of X-linked traits in women than in men. See also: gene dosage compensation Synonym(s): Lyon hypothesis, X-inactivation. [M. Lyon] Lyon hypothesis See X-INACTIVATION. Lyon hypothesis see INACTIVE-X HYPOTHESIS. Lyon, Mary F., English cytogeneticist, 1925–. Lyon hypothesis - Synonym(s): lyonizationlyonization - the normal phenomenon that wherever there are two or more haploid sets of X-linked genes in each cell, all but one of the genes are inactivated, apparently at random, and have no phenotypic expression. Synonym(s): Lyon hypothesis; X-inactivation LegalSeeHypothesis
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