lyonization


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lyonization

 [li″on-ĭ-za´shun]
the process by which or the condition in which all X chromosomes of the cells in excess of one are inactivated on a random basis.

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.
[M. Lyon]

lyonization

/ly·on·iza·tion/ (li″on-ĭ-za´shun) the process by which or the condition in which all X chromosomes of the cells in excess of one are inactivated on a random basis.

lyonization

[lī′ənīzā′shən]
Etymology: Mary L. Lyon; Gk, izein, to cause
the process of random inactivation of one of the X chromosomes in the cells of females to compensate for the presence of the double X gene dose. See also Lyon hypothesis.

lyonization

Genetics A normal genetic event that consists of inactivation of all X chromosomes–portions of the 'inactivated' chromosome may remain functional if in excess of one

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]

Lyonization

See X-INACTIVATION.

Lyon,

Mary F., English cytogeneticist, 1925–.
Lyon hypothesis - Synonym(s): lyonization
lyonization - 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

lyonization

the process by which or the condition in which all X chromosomes of the cells in excess of one are inactivated on a random basis.
References in periodicals archive ?
This carrier status, together with an extreme lyonization, appears to explain the clinical phenotype of CGD with severe recurrent infections.
The late onset of this patient's CGD could perhaps be explained by age-related skewing of lyonization (10).
Increased susceptibility of a carrier of X-linked chronic granulomatous disease (CGD) to Aspergillus fumigatus infection associated with age-related skewing of lyonization.
In addition to biological explanations, technical reasons may account for some of the discrepancies in the estimation of skewed lyonization in healthy females and possibly clonality analysis in various malignancies.
T lymphocytes were also studied in females with a skewed pattern of lyonization or when results were discordant.
The incidence of excessive lyonization by age group was: 9 of 38 (24%) in neonates, 0 of 46 in women <50 years, and 6 of 29 (21%) in women >50 years of age (Table 2).
By analysis of RNA polymorphism: Percentage of X-skewed lyonization was 3%, 0%, and 21% in the different groups respectively (Table 2).
In these two patients, a random pattern of X-inactivation was obtained in nucleated cells by using HUMARA polymorphism, whereas a clonal hematopoiesis was observed by transcript analysis in all fractions except T lymphocytes in one patient, and a skewed lyonization in the other patient.
Comparison between the DNA and RNA polymorphisms showed some interesting results that may help clarify the interpretation of excessive lyonization in healthy females.
A somatic tissue not involved in the disease process and embryologically related to the sample must be chosen to eliminate excessive lyonization or acquired skewing.