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A genetic disorder is a disorder that results from an abnormality in a person's genome. The abnormality can be something very tiny to very major. Some genetic disorders are the result of acquired mutations or changes in a preexisting group of genes or single gene, while other disorders are inherited by an individual's parents. Mutations can occur either because of environmental exposure or randomly.
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Types of Inheritance
Monogenetic or Mendelian inheritance, or single gene inheritance, is a result of mutations or changes occurring in the DNA sequence of one gene. There are more than 6,000 genetic disorders which are classified as single-gene, and these affect about one out of 200 babies born. These are referred to as monogenetic disorders. Some examples include cystic fibrosis, Marfan syndrome, hemochromatosis, sickle cell anemia and Huntington's disease. Monogenetic disorders have recognizable inheritance patterns, including autosomal recessive, autosomal dominant and X-linked.
Multifactorial Inheritance is also referred to as polygenic or complex inheritance and results from a combination of multiple gene mutations and environmental factors. Examples include heart disease, Alzheimer's disease, diabetes, obesity, high blood pressure, arthritis and cancer.
Chromosomal means a chromosomal abnormality is the cause. Chromosomes carry genetic materials. Examples include trisomy 21 or Down syndrome.
A rare type of genetic disorder is the mitochondrial type that results from mutations in the nonchromosomal DNA of mitochondria.
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If a genetic mutation is in a sex chromosome, the disorder that results will affect females and males differently. For example, some disorders may affect males only slightly, but females severely, while other disorders may affect females only slightly, but males severely.
Certain genetic disorders are caused by a combination of both mutations in several genes and environmental factors. This makes the majority of these disorders multifactorial inheritance disorders.
Multifactorial inheritance also plays a role in human traits, such as height, skin color, fingerprint patterns and eye color. These are what are known as heritable traits.
There are literally thousands of identified genetic disorders. Most are rare. They will only affect about one person out of several thousand or more than several thousand. One example is cystic fibrosis, a common autosomal recessive disorder. Approximately five percent of Americans carry a copy of the defective gene necessary to cause this genetic disorder.
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Human Genome Project Information. (2008). Genetic Disease Information. Retrieved on March 29, 2011 from the Human Genome Project Information: http://www.ornl.gov/sci/techresources/Human_Genome/medicine/assist.shtml
National Human Genome Research Institute. (2011). Frequently Asked Questions About Genetic Disorders. Retrieved on March 29, 2011 from the National Human Genome Research Institute: http://www.genome.gov/19016930
The University of Utah Genetic Science Learning Center. (2011). What are Genetic Disorders? Retrieved on March 29, 2011 from The University of Utah Genetic Science Learning Center: http://learn.genetics.utah.edu/content/disorders/whataregd/
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