Hereditary genetic disorders

In hereditary genetic disorders, a mutated gene (one with changes in the DNA) that causes disease is passed down through generations of a family. Genes carry the instructions (DNA) to build the proteins your body needs, and changes in the genetic code can alter the proteins that are made, which can lead to disease.

There are three types of genetic disorders:

• Single gene disorders are caused by a mutation in a single gene. The mutation may be present on one or both chromosomes (one chromosome inherited from each parent). Sickle cell disease, cystic fibrosis and fCJD are examples of single gene disorders.
• Chromosome disorders are caused by an excess or deficiency of the genes that are located on chromosomes, or structural changes within chromosomes. Down syndrome, for example, is caused by an extra copy of chromosome 21, but no individual gene on the chromosome is abnormal.
• Multifactorial inheritance disorders are caused by a combination of small variations in genes, often in concert with environmental factors. Most genetic disorders are multifactorial inheritance disorders. Heart disease and most cancers are examples of these disorders. Both sporadic and variant CJD appear to have a multifactorial interaction of genes and environment.

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