A genetic disease is a medical condition caused by changes or mutations in an individuals DNA sequence. There are three types of genetic disorders: single-gene disorders, chromosomal disorders, and complex disorders.
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Single-gene disorders are caused by defects in one particular gene. There are over 10,000 human disorders caused by a change, known as a mutation, in a single gene. Individually, single-gene disorders are each very rare, but as a whole, they affect about one per cent of the population.
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Chromosomal disorders result from changes in the number or structure of the chromosomes. Changes in the number of chromosomes happen when there are more or fewer copies of a particular chromosome than usual. Changes in chromosome structure happen when the material in an individual chromosome is disrupted or rearranged in some way. This may involve the addition or loss of parts of a chromosome.
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Complex disorders (also known as multifactorial or polygenic) are those that are caused by the simultaneous effect of many different genes, often in a complex interaction with environmental and lifestyle factors such as diet.
Genetic disorders can be inherited from one or both parents, or they can occur due to mutations that happen during a persons lifetime. Genetic tests on blood and other tissue can identify genetic disorders.
