Genetics
Alternate Names : Genetic Markers, Heredity and Disease, Heritable, Heterozygous, Homozygous, Inheritance, Inheritance Patterns
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Chromosomal disorders
In chromosomal disorders, the defect is due not to a single gene, but to an excess or deficiency of the genes contained in a whole chromosome or chromosome segment.
Down syndrome is the most common chromosomal disorder (1 out of 800). Affected individuals have an extra copy of chromosome 21. This unbalanced set of genes results in mild to moderate mental retardation and numerous physical changes. Other common examples are Klinefelter syndrome (1 out of 1,000 males) and Turner syndrome (1 out of 5,000 females).
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