Levene died in 1940, before the true significance of DNA became clear. Levene is known for his tetranucleotide hypothesis (formulated around 1910) which first proposed that DNA was made up of equal amounts of adenine, guanine, cytosine, and thymine.
Alzheimer's is not just a disease of old age. Younger-onset (also known as early-onset) Alzheimer's affects people younger than age 65.Up to 5 percent of the more than 5 million Americans with Alzheimerâs have younger-onset.eople who have early onset Alzheimer's may be in any stage of dementia â early stage, middle stage or late stage. The disease affects each person differently and symptoms will vary. If you are experiencing memory problems: 1  Have a comprehensive medical evaluation with a doctor who specializes in Alzheimer's disease.
â¢ One in nine people age 65 and older (11 percent) has Alzheimerâs disease. â¢ About one-third of people age 85 and older (32 percent) have Alzheimerâs disease. â¢ Of those with Alzheimerâs disease, the vast majority (81 percent) are age 75 or older. An estimated 4 percent are under age 65, 15 percent are 65 to 74, 44 percent are 75 to 84, and 37 percent are 85 or older.