Alzheimer's disease is a neurodegenerative disease affecting memory, cognitive and non-cognitive functions. Studies show that most cases of Alzheimer's disease affect people aged 60 or older; while 80% of these cases are due to genetics. The risk of suffering from Alzheimer's disease varies depending on age and ethnicity. That being said, some older adults contract this disease very late in life, as they approach age 90. The gene that is usually responsible for Alzheimer's disease (AD) is apolipoprotein E (APOE gene), which takes its name from the protein coding. Apolipoprotein. It is found on chromosome 19 and has three main alleles on the gene that appear to be responsible for this disease. These are: ε2, containing cysteine ​​at position 112 and arginine at position 158 of the gene, ε3 containing cysteine ​​at positions 112 and 158, and ε4 containing arginine at positions 112 and 158 of the gene . The APOE ε4 allele is the most common allele in the disease. The APOE ε4 allele is the most common allele in the disease. The function of this gene is to regulate cholesterol and triglyceride metabolism. This shows that it is not a simple coincidence that high cholesterol and diabetes lead to late onset of Alzheimer's disease. The APOE ε4 allele was tested and found to be very dangerous in 1993. Since then, many other studies have been done on this allele and it is known to be the main cause of Alzheimer's disease. Human Genome Project, a DNA microarray system used to study more than 80% of the Caucasian genome for association signals, called Affymetrix's 500K GeneChip, was created. This microarray kit was used to confirm that by using a single high-density core...... middle of paper ......sion, the results point researchers in the right direction, proving that the late onset of Alzheimer's disease is very closely linked to this APOE locus, in particular the ε4 allele. Further studies may also show that this allele will likely contribute to other diseases as well. Through the use of an ultra-high density genome, further associations will be established regarding the link between late onset Alzheimer's disease and the APOE locus. Works Cited Coon, Keith D. Ph.D.; Amanda J. Myers, Ph.D.; David W. Craig, Ph.D.; Jennifer A. Webster, BA; John V. Pearson, B.Sc.; Diane Hu Lince, Ph.D.; Victoria L. Zismann, MS; Thomas G. Beach, MD; Doris Leung, MD “High-density whole-genome association study reveals APOE as the major susceptibility gene for late-onset sporadic Alzheimer's disease. » Postgraduate Press for Physicians. J Clin Psychiatry 68:4, April 2007: 613-618. (Print)