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.
Age: The risk of developing Alzheimerâs increases with age. One out of every 10 persons 65 years and older is a victim of Alzheimer's disease, although early-onset victims may be in their 40s and 50s. Approximately 20 percent of Americans between the ages of 75 and 84, and almost half of those 85 years and older suffer from Alzheimer's disease.