Re: What can you tell my class about specific mutations in the Amish culture?

Many isolated groups- isolated because of geography, religious preference, etc.- show a higher rate of rare genetic diseases than the population at large. This is due to founder effect: one or more ancestors carried the mutation causing the disease, and because of inbreeding due to isolation, the mutant copy was propogated. This is the case with the Amish and other Anabaptist groups in the U.S.

In searching the net and through textbooks I could find nothing on a fifth finger syndrome in the Amish. I did find out some other neat stuff, though:
•Amish Genetic Diseases. This site has info on one very rare disease seen more prevalently in the Amish, called Glutaric Acidemia. This is a metabolic disorder that can cause brain damage if not treated properly.
•There's a form of dwarfism seen in the Amish as well, called Ellis- van Creveld syndrome. It's recessive, and in addition to the dwarfism, patients also have short fingers and hypoplastic (small) nails.

You can consult Thompson and Thompson's Genetics in Medicine textbook, fifth edition, published in 1991 by Saunders, for more information on inbreeding and recessive diseases.