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.
When people are diagnosed with Alzheimerâs at about age 60 or 65, they generally decline more slowly. Their life expectancy is then on the order of 12 or 14 years, and some may even live up to 20 years longer. But when people are diagnosed at age 80 or 85, their Alzheimerâs tends to progress more rapidly. Their advanced age also increases the probability of their death, and they generally survive only 5 to 8 years.