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Alzheimer's Disease and Heredity
Scientists recognize that Alzheimer's Disease has two forms:
The relationship between Alzheimer's Disease and heredity is complicated. In understanding the role of heredity in Alzheimer's Disease, it is helpful to define some terms which explain how human characteristics are passed from generation to generation: Chromosomes: Rod-like structures found in all cells of the body Each individual has a total of 46 chromosomes in 23 pairs. Under normal circumstances, each person receives one chromosome of a pair from his/her mother and the other from his/her father. Genes: The basic units of heredity that allow specific attributes or characteristics to be passed from one generation to the next. Each chromosome carries genes which are like beads on a string. Allele: Alternative forms of a gene Each attribute or characteristic can have 2 or more alleles. For example, a given characteristic may have two forms of the gene, or two alleles, "A" and "a". The combination of alleles (e.g. AA, Aa, or aa), one of which comes from the mother and one from the father, determines what characteristics or attributes will be expressed and what alleles will be subsequently passed on to future generations. Mutations: Genes that have undergone a process of change. Once a mutation occurs, it can be passed on from generation to generation. Mutations can result in a disease or a disease susceptibility being expressed; mutations can also have not visible effects. A family history of Alzheimer's Disease Research indicates that individuals with a family history of Alzheimer's Disease (e.g. an affected parent or brother/sister) have a greater chance of developing the disease compared to persons having no affected relatives. Determination of the chance of risk of developing Alzheimer's Disease is difficult. A family history of Alzheimer's Disease does not imply the familial autosomal dominant type of the disease. Separating the role of genes from that of other nongenetic factors such as toxic agents, viruses, head injuries, etc. is difficult. It may well be that in most families, inherited susceptibility and a particular "trigger" are both required before an individual develops the disease. What are scientists doing in order to learn more about family history and Alzheimer's Disease? Individual data
Last Updated June 20, 2005 |
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