Genetic disorder facts for kids
A genetic disorder is an illness caused by abnormalities in the genome. They are heritable, and are passed down from the parents' genes. If a genetic disorder is present from birth, it is a type of congenital defect. Some only show up in later life.
Most genetic disorders are quite rare and affect one person in every several thousands or millions. Sometimes they are relatively frequent in a population. These types of recessive gene disorders give an advantage in certain environments when only one copy of the gene is present. Sickle cell anaemia is an example.
The same disease, such as some forms of cancer, may be caused by an inherited genetic condition in some people, by new mutations in other people, and by nongenetic causes in still other people. A disease in only called a genetic disease when it is inherited.
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Chromosomes in Down syndrome, the most common human condition due to aneuploidy. There are three chromosomes 21 (in the last row).
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Hereditary defects in enzymes are generally inherited in an autosomal fashion because there are more non-X chromosomes than X-chromosomes, and a recessive fashion because the enzymes from the unaffected genes are generally sufficient to prevent symptoms in carriers.
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On the other hand, hereditary defects in structural proteins (such as osteogenesis imperfecta, Marfan's syndrome and many Ehlers–Danlos syndromes) are generally autosomal dominant, because it is enough that some components are defective to make the whole structure dysfunctional. This is a dominant-negative process, wherein a mutated gene product adversely affects the non-mutated gene product within the same cell.
See also
In Spanish: Enfermedad genética para niños
