People who have a parent or sibling that has Alzheimers disease are 2-3 times more likely to develop the disease than those with no family history of it. Being related to a person with the disease increases likelihood of developing it and is now thought to be 80% genetic. Scientists have identified 10 kinds of genes that have been linked to Alzheimers disease most of which have been discovered since 2009. the first gene discovered thought to be a risk gene to AD is ApoE 4. another but more rarer gene is the deterministic gene, they are only found in a few hundred extended families around the world.
If a person has this gene they are more likely to develop it at younger age but would undoubtedly develop it. Genes for the onset of AD have been identified on chromosome and 14 and genes associated with the late onset of AD have also been found on chromosome 10. an evaluation point of family history and genes is that it could lead to more effective treatment of AD. The genes identified affect bodily processes which could become targets for treatments. Nee reported on a family with 531 family members.
53 were identified as suffering from the disease, which suggests that there is some contributing genetic factor. However it could be said that it is due to the environment which they all share, which are the same conditions, same social class and quality of living. It then makes it hard to differentiate between nature and nurture. Hendrie studied Yoruba people of Nigeria and compared then with Americans. Both had similar frequency of genes linked to AD but the Yoruba suffered much less from the disorder.
This tells us that other factors must be involved. Perhaps it may be the diet of the Yoruba which is low in salt, fat and calories which reduces the risk. However it could be explained by the interactionist approach and the stress diathesis approach. However even with al the conflicting evidence genes as an explanation for AD must still be taken seriously and scientist shave found that mutations in certain genes lead to plaques in the brain which then leads to death of nerve cells and the onset of AD.
Brain abnormalities autopsies have revealed differences in the brains of people with AD when compared to one without it. These abnormalities are thought to be the cause of the disorder. Plaques are deposits of a beta amyloid 42 protein that build up in the spaces between the neurons. These cause problems in the communication between neurons. Tangles are deposits of the protein tau that accumulate inside the nerve cells.