Study of a family with a fragile site of the X chromosome at Xq27–28 without mental retardation

1989 ◽  
Vol 81 (4) ◽  
pp. 353-357 ◽  
Author(s):  
M. A. Voelckel ◽  
N. Philip ◽  
C. Piquet ◽  
M. C. Pellissier ◽  
I. Oberlé ◽  
...  
Keyword(s):  
Mental Retardation ◽  
X Chromosome ◽  
Fragile Site

Fragile Sites on Chromosomes

PEDIATRICS ◽  
1982 ◽  
Vol 69 (1) ◽  
pp. 121-123
Author(s):  
Frederick Hecht ◽  
Thomas W. Glover ◽  
Barbara Kaiser-Hecht
Keyword(s):  
Mental Retardation ◽  
X Chromosome ◽  
Fanconi Anemia ◽  
Ataxia Telangiectasia ◽  
Autosomal Recessive ◽  
Fragile Site ◽  
Chromosome Instability ◽  
Chromosome Complement ◽  
Fragile Sites ◽  
Chromosome Fragility

A fragile site on the X chromosome is associated with a common form of mental retardation in males and a proportion of females.1-3 This association was not fully appreciated when the fragile site on the X was first described in 1969,4 but it is crystal-clear today. Chromosome fragility can be random, as in Fanconi anemia, Bloom syndrome, and ataxia-telangiectasia, the chromosome instability syndromes.5 Breaks and rearrangements of chromosomes are seen in these disorders, all of which are autosomal recessive conditions predisposing to cancer. Fragile sites are special spots in the genome where gaps and breaks occur nonrandomly. The balance of the chromosome complement is normal.

Health Supervision for Children With Fragile X Syndrome

PEDIATRICS ◽  
1996 ◽  
Vol 98 (2) ◽  
pp. 297-300
Author(s):  
Keyword(s):  
Mental Retardation ◽  
Developmental Delay ◽  
Fragile X Syndrome ◽  
X Chromosome ◽  
Dna Analysis ◽  
Fragile Site ◽  
Fragile X ◽  
Physical Features ◽  
Relationship Of ◽  
The Relationship

This set of guidelines is designed to assist pediatricians in caring for children with fragile X syndrome confirmed by DNA analysis (Table). Occasionally pediatricians are called on to advise a pregnant woman who has been informed of a prenatal diagnosis of fragile X syndrome. Therefore, guidelines are also offered for this situation. Fragile X syndrome is usually diagnosed during childhood and is characterized by developmental delay or mental retardation, characteristic physical features, and abnormal behavioral patterns.1,2 The distinctive fragile site on the X chromosome was first described in 1969 as a discontinuous site on the long arm of the X chromosome present after cell culture under folate-deficient conditions. In 1977 the relationship of this site to X-linked mental retardation was noted, and fragile X syndrome began to be defined. Since that time, the cytogenetic, molecular, and clinical features of the condition have been more clearly defined,3 and it is now recognized as the most common hereditary cause of mental retardation. Its frequency has been estimated to be approximately per 2500 to 1 per 1250 males and 1 per 5000 to 1 per 1600 females. The phenotype of fragile X syndrome in males often has a number of distinctive, recognizable features, including developmental delay or mental retardation, a prominent forehead, a long, thin face and a prominent jaw that appear late in childhood or early adolescence, large protuberant and slightly dysmorphic ears, and the presence of or ultimate development of macro-orchidism. This phenotype can be very subtle, is not always apparent, and becomes more identifiable with age.2

X-linked mental retardation, macro-orchidism, and the Xq27 fragile site

1980 ◽  
Vol 96 (5) ◽  
pp. 837-841 ◽  
Author(s):  
Gillian Turner ◽  
Art Daniel ◽  
Michael Frost
Keyword(s):  
Mental Retardation ◽  
Fragile Site

scholarly journals 761 MULTIPLE SIBLING MENTAL RETARDATION AND THE IMPACT OF THE FRAGILE X CHROMOSOME

1981 ◽  
Vol 15 ◽  
pp. 569-569 ◽  
Author(s):  
Lawrence R Shapiro ◽  
Murray D Kuhr ◽  
Patrick L Wilmot
Keyword(s):  
Mental Retardation ◽  
X Chromosome ◽  
Fragile X ◽  
The Impact

Cytogenetics of three breeds of river buffalo (), with evidence of a fragile site on the X chromosome

1998 ◽  
Vol 49 (3) ◽  
pp. 529-538 ◽  
Author(s):  
R.M.L Pires ◽  
R.H Reichert ◽  
S Kasahara
Keyword(s):  
X Chromosome ◽  
Fragile Site ◽  
River Buffalo

A Role for the X Chromosome in Sex Differences in Variability in General Intelligence?

2009 ◽  
Vol 4 (6) ◽  
pp. 598-611 ◽  
Author(s):  
Wendy Johnson ◽  
Andrew Carothers ◽  
Ian J. Deary
Keyword(s):  
Sex Differences ◽  
Mental Retardation ◽  
X Chromosome ◽  
Cognitive Abilities ◽  
Population Distribution ◽  
Population Variation ◽  
General Intelligence ◽  
Substantial Evidence ◽  
Normal Distributions ◽  
Intellectual Abilities

There is substantial evidence that males are more variable than females in general intelligence. In recent years, researchers have presented this as a reason that, although there is little, if any, mean sex difference in general intelligence, males tend to be overrepresented at both ends of its overall distribution. Part of the explanation could be the presence of genes on the X chromosome related both to syndromal disorders involving mental retardation and to population variation in general intelligence occurring normally. Genes on the X chromosome appear overrepresented among genes with known involvement in mental retardation, which is consistent with a model we developed of the population distribution of general intelligence as a mixture of two normal distributions. Using this model, we explored the expected ratios of males to females at various points in the distribution and estimated the proportion of variance in general intelligence potentially due to genes on the X chromosome. These estimates provide clues to the extent to which biologically based sex differences could be manifested in the environment as sex differences in displayed intellectual abilities. We discuss these observations in the context of sex differences in specific cognitive abilities and evolutionary theories of sexual selection.

DNA studies of X-linked mental retardation associated with a fragile site at Xq27

1986 ◽  
Vol 23 (1-2) ◽  
pp. 633-642 ◽  
Author(s):  
Kay E. Davies ◽  
John M. Opitz ◽  
James F. Reynolds
Keyword(s):  
Mental Retardation ◽  
Fragile Site
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