Genetic disorder

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Genetic disorders are not curable, but their symptoms may be ameliorated by various medical actions.

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Causes

There are several causes for genetic disorders to appear. The most common ones include:

  • A mutation in one or more genes, affecting their functions.
  • Abnormal chromosome number, as in Down syndrome.
  • Triplet expansion repeat mutations, causing the modification of gene expression or a gain of function.
  • Defective genes, which are commonly inherited from parents.

The list of genetic diseases currently includes about 4,000 cataloged and described affections, but the list is growing. Top of the list at the moment is the cystic fibrosis, with its gene carried by 5% of the population in the US alone.

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Types

There are three types of genetic disorders: single-gene disorders, multifactoral and polygenic disorders, and chromosomal disorders, occurring because of affections at different levels.

  • Single-gene disorders appear due to the mutation of a single gene, that causes a protein or enzyme not to be produced. The effects of these changes can vary greatly, from harmless ones like color blindness to lethal affection like the Tay-Sachs disease. Their inheritance can be autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, Y-linked or mitochondrial.
  • Multifactoral and polygenic disorders are appear due to mutations in more genes, sometimes associated with some environmental factors. The canonical example is the diabetes, which is hereditary, but there is no obvious pattern of inheritance.
  • Chromosomal disorders affect entire chromosomes and they are often very severe, causing growth problems and impairment of the body's development and system functions. They are commonly caused by changes in the number of chromosomes, randomly occurring during the formation of the ova and sperm cells, but they can also appear due to changes in chromosome structure. These kind of changes usually occur due to the breakage and reunion of the chromosome segments, either when the reproductive cell is formed or in the early development of the fetus.
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Treatment

The genetic affections themselves are incurable, but treatment to ameliorate their symptoms does exist. Such a treatment is performed by geneticists, while physicians and patients are counseled by genetic counselors.

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