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.
1 But Alzheimer's is not just a disease of old age. 2  Up to 5 percent of people with the disease have early onset Alzheimer's (also known as younger-onset), which often appears when someone is in their 40s or 50s. 3  Learn more: Early Onset Alzheimer's and Risk Factors.4  Alzheimer's worsens over time.lzheimer's and dementia basics. 1  Alzheimer's is the most common form of dementia, a general term for memory loss and other intellectual abilities serious enough to interfere with daily life. 2  Alzheimer's disease accounts for 60 to 80 percent of dementia cases.