The presence of three or more minor and/or major anomalies in an individual with mental retardation may indicate not just a developmental relationship between the retardation and malformation syndromes, but a common cause for the entire retardation malformation syndrome. Tables, Bibliography. (Author)

Reviewed are chromosomal anomalies affecting one's eyes. Brief descriptions are given of the genetic etiology of bilateral retinoblastoma (malignant tumors), aniridia (absence of the iris), cataracts, congenital glaucoma, Reginitis Pigmentosa (progressive deterioration of the visual cells), Choroidermia (degeneration of the vascular coat of the…

The need to counsel patients with genetic ophthalmological problems is stressed in the article. Assessment of autosomal dominance or autosomal recessitivity in an individual is explained and sex-linked heredity is traced. Practical examples of genetic abnormalities, such as pigmentary retinopathy and chorodineremia, are discussed. (PHR)

Research points to two distinct regions within the Prader-Willi chromosome region: one for Prader Willi syndrome and one for Angelman syndrome. Genetic mechanisms in Angelman syndrome are complex, and at present, three mechanisms are recognized: maternal deletion, paternal uniparental disomy, and a nondeleted nondisomic form. (Author/JDD)

Sotos syndrome is characterized by high birth length, rapid bone growth, distinctive facial features, and possible verbal and motor delays. It is more common in males than females. Developmental deficits, specific learning problems, and speech/language delays may also occur. (DB)

This article discusses inheritance patterns in hearing loss, epidemiology, clues to genetic causes, locating genes that cause hereditary disorders, genes related to hearing loss disorders in individuals with Usher syndrome, Waardenburg syndrome, Treacher-Collins syndrome, Branchio-oto-renal and Pendred syndromes, and the significance of finding…

This fact sheet uses a question-and-answer format to summarize what is known about the genetic causes of mental retardation. Questions and answers address the following topics: what genetics is; how a person's genes can cause mental retardation; how often mental retardation is inherited (up to 60 percent of severe mental retardation has genetic…

Fragile X syndrome is an inherited genetic condition identified by a break or a weakness on the long arm of the X chromosome, and associated with mental retardation. Described on this single-sheet information guide are the prevalence of fragile X syndrome, its increased rate of incidence in boys as compared to girls, physical characteristics,…

The paper refutes the long held belief that Down's syndrome is the result of maternal age and maternal etiology. The author cites new evidence which demonstrates that Trisomy-21 (the presence in the chromosome of an extra arcocentric chromosome resulting from non-disjunction), the major cause (95% of the cases) of Down's syndrome, can originate in…

Reported are seven cases in two families of the Meckel syndrome, whose key features are occipital encephalocele, cleft lip and palate, polydactyly, and polycystic kidneys. Evidence supports the hypothesis that the syndrome is a recessively inherited condition, determined by homozygous expression of a single autosomal gene. (Author/KW)

A case study is presented of a boy with partial tetrasomy 15, severe mental retardation, and autism, from age 6 to 9. The case is analyzed in relation to other cases with an extra marker chromosome 15 and the mechanisms that underlie the association between autism and marker chromosome 15. (JDD)

Presents current findings and theories on the causes of Down Syndrome. Reviews research which focused on chromosome 21 and the pathologies associated with it. (ML)