Plaques, Tangles, and Genes

What Is Alzheimer’s Disease?
3.14 minutes

Scientists believe that, for most people, Alzheimer’s disease results from a combination of genetic, lifestyle, and environmental factors that affect the brain over time.

Less than 5 percent of the time, Alzheimer’s is caused by specific genetic changes that guarantee a person will develop the disease.

While the causes of Alzheimer’s are not yet fully understood, its effect on the brain is clear. Alzheimer’s disease damages and kills brain cells. A brain affected by Alzheimer’s disease has many fewer cells and many fewer connections among surviving cells than does a healthy brain.

As more and more brain cells die, Alzheimer’s leads to significant brain shrinkage. When doctors examine Alzheimer’s brain tissue under the microscope, they see two types of abnormalities that are considered hallmarks of the disease:

These clumps of a protein called beta-amyloid may damage and destroy brain cells in several ways, including interfering with cell-to-cell communication. Although the ultimate cause of brain cell death in Alzheimer’s isn’t known, abnormal processing of beta-amyloid is a prime suspect.

Brain cells depend on an internal support and transport system to carry nutrients and other essential materials throughout their long extensions. This system requires the normal structure and functioning of a protein called tau. In Alzheimer’s, threads of tau protein twist into abnormal tangles, leading to failure of the transport system. This failure is also strongly implicated in the decline and death of brain cells.


Alzheimer’s genes increase the the risk of developing Alzheimer’s disease. Genes control the function of every cell in your body. Some genes determine basic characteristics, such as the color of your eyes and hair. Other genes can make you more likely to develop certain diseases — including Alzheimer’s.

Researchers have identified several Alzheimer’s genes — genes that are associated with Alzheimer’s disease. But genetic risk factors are just one part of the Alzheimer’s story, a complex narrative that scientists continue to try to unravel.



Mayo Clinic Staff. “Alzheimer’s Disease: Overview.” Mayo Foundation for Medical Education and Research, 30 Dec. 2017,

Mayo Clinic Staff. “Alzheimer’s Genes: Are You at Risk?” Mayo Foundation for Medical Education and Research, 26 Jan. 2016,

“What Is Alzheimer’s Disease?” YouTube, uploaded by actionalz, 26 Aug. 2008,

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