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Genetic Mutations & Dementia: Information - DementiaGuide.com
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About Dementia
Types of Dementia

Genetic Mutations

Some forms of dementia are linked to genetic mutations. To understand genetic mutations, it is best to first talk about what a gene is. Genes are made up of DNA , which exists in most of the billions of cells each with its own nucleus

A part of a cell where genetic information about a person is stored.

that make up our bodies. The nucleus contains information about how our entire body functions in the language of DNA. DNA is organized into units called chromosomes which we inherit from our parents. We have 46 chromosomes, 23 from your mother and 23 from your father, which match up to make 23 pairs of chromosomes. These 23 pairs of chromosomes exist in each of our cells and each chromosome carries hundreds or thousands of genes. A gene is a DNA sequence that contains the information for the production of a particular protein . In order to make a protein, DNA needs to be translated into another language called RNA . This is similar to translating a sentence from English to French. The content and information remains the same but the language is different.

DNA, RNA & Proteins

The next step is to join together amino acids to create a functional protein. RNA is like a code that tells the body which amino acids to string together to build a protein. Therefore, a gene acts as a blueprint for the production of a particular protein. Genes direct almost every aspect of the operation of our body. They contain the information that determines our hair and eye colour and other traits which we inherited from our parents. A variation or a mutation in a gene can cause a slight difference in the protein produced and sometimes a change in the protein's function.

A genetic mutation is a permanent change to a gene that can be caused by external factors such as UV light, radiation and X-rays or from errors that can occur when a cell is dividing to make more cells. Once a mutation occurs, it can be passed down to children. Mutations can disrupt or stop the normal functioning of a gene.

With Alzheimer's disease , 4 genes have been identified that affect its development.Three of these genes (the amyloid precursor protein (APP ) gene, presenillin gene (PSEN-1), and presenillin gene (PSEN-1)) affect younger people, while one other (apolipoprotein E (APOE )) affects older people. It is important to note, however, that these genetic reasons for Alzheimer's disease are very rare and account for less than 1 in 1000 cases of the disease.

Similarly, a number of very rare forms of vascular dementia are caused by genetic mutations. For example, cerebral automsomal dominant arteriopathy with subcortical infarcts and leukoencephalopahth (CADASIL ) is the result of a mutation on the Notch 3 gene. Some people with Frontotemporal Dementia (FTD) or with Creutzfeldt-Jakob Disease seem to have a very strong family history of these diseases, suggesting a genetic link.

Especially with cases that occur in older people (over 65 years) the role of specific genes is less clear. In most memory clinics, fewer than 5% of patients meet the definition for Alzheimer's disease that is caused by a genetic mutation.

See Also:
About Dementia > Alzheimer's Disease > Is Alzheimer's Disease Inherited?
About Dementia > Types of Dementia > Vascular Dementia
About Dementia > Types of Dementia > Frontotemporal Dementia
About Dementia > Types of Dementia > Alzheimer's Disease
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Last updated December 7, 2018
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