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.
Of all the people who have Alzheimer's disease, about 5 percent develop symptoms before age 65. So if 4 million Americans have Alzheimer's, at least 200,000 people have the early-onset form of the disease.Early-onset Alzheimer's has been known to develop between ages 30 and 40, but that's very uncommon.ome people with early-onset Alzheimer's have the common form of the disease, and experts don't know why these people get the disease at a younger age than others do.