The New York Times has a powerful story about the genetics of early onset Alzheimer's disease, by Gina Kolata: "An Alzheimer's gene: one family's saga".
Gary was pretty sure it was his family whose gene had been found.
He got a copy of Science and turned to the article, which included a family tree with members who had the gene represented by black diamonds. Those who did not have the gene were represented by white diamonds.
It was scary even to look. Gary knew every person in that diagram, and he knew he was there too. Would he be a black diamond or a white one?
The story focuses on one very large family in which onset at age 50 was clearly caused by a Mendelian dominant. But in addition to this, it gives a perspective on how the science works, where unraveling rare Mendelian causes for the disorder helps identify the pathways by which more common -- and more complex -- multigenic cases of the disorder may work.