The Genetic Drift Webquest
The Amish in the US began as a small group of Swiss-Germans that immigrated to the US in the 1700’s. Over the course of a few centuries they grew from a small founding population of 200 to a current population of more than 250,000. The most interesting thing about the Amish is that it’s a religious group that has remained culturally isolated and by extension, genetically isolated from the rest of the country. This genetic isolation from other humans has lead to an unprecedented amount of genetic disorders among the Amish.
Physicians were initially exposed to the genetic problems plaguing the Amish in the 1960’s. When the Amish began to reach out to the medial community doctors discovered that there were an unusual number of rare genetic diseases. One of these visible and rare genetic disease was called Ellis-Van Creveld syndrome. What was surprising to medical geneticists was not the presence of the rare genetic disease but rather how many Amish had the disease in the first place. Basically, the Amish in Lancaster County, Pennsylvania had more cases of Ellis-Van Creveld syndrome than all other human in the world combined! What was even more surprising was the fact that there was not just one rare genetic disease but rather dozens of rare genetic disease (In this context, rare genetic disease means that there may be less than 150 humans in the planet having the disease). Even more unfortunate is the fact that there are hundreds of other genetic disease associated with the Amish.
The big question that the Amish wanted to know was, why do they seem to have an unusual share of genetic disease when compared to the non-Amish and how do they stop those genetic disease in the first place!
What you are doing
Your task will be to investigate a rare genetic disorder found among the Amish and to use evolutionary theory to both, help you understand why genetic disease can become common among isolated populations and to see how evolutionary theory can assist in curbing prevalence of genetic disease.
Before you begin your task make sure you do the following things.
Read lecture notes on evolution. Especially the ones pertaining to Genetic drift.
Watch video on Amish genetic diseases.
What you need to do
Before you begin this assignment, I recommend that you clearly understand what evolution is (a change in allele frequency from one generation to the next). Make sure you use the information provided and give me informed ideas that are based on your understanding of the subject matter. For this assignment you will have to answer the following items (1 page):
Pick and a rare genetic disorder that is common among the Amish and tell me how common the disease is around the world vs among the Amish? Give me estimated percentage of afflicted individuals! (I don’t need to know details of the genetic disease just its name). The important idea is to understand why disease associated alleles are found in high frequencies in the first place!
Explain in evolutionary terms why the genetic disorder that you investigated is found in unusually high frequencies among the Amish in the first place. You will need to give me one evolutionary mechanism that can specifically explain the Amish issue. Make sure you name the evolutionary mechanism and give a quick explanation of how the evolutionary mechanism works.
Explain how the Amish might be able to curtail the incidence of your chosen genetic diseases using evolutionary knowledge. You will need to give me one evolutionary mechanism that would be able to fix the Amish dilemma. Make sure name the evolutionary mechanism and give a quick explanation of how the evolutionary mechanism would be able to work.
Lastly, remember to cite all your work!