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Founder Mutations [Preview]

A special class of genetic mutations that often cause human disease is enabling scientists to trace the migration and growth of specific human populations over thousands of years

The extensive length of the modern haplotype indicates that the founder mutation is quite young. Exactly how young has been a subject of much discussion among scientists. The methods for estimating the age of these mutations make a number of assumptions and give us an age range, rather than an exact age. In the case of the hemochromatosis mutation, the majority of the estimates suggest that it arose 60 to 70 generations ago, around A.D. 800 and long after the fall of the Roman Empire. Such a young age suggests that our founder mutation most likely originated in northwestern Europe and spread southward. Other evidence, including the mutations high frequency in Norway, has led to an alternative hypothesis that it is older, perhaps even predating the Roman Empire. Further use of DNA markers in European populations is likely to settle this question.

Anthropologists, notably Luigi Luca Cavalli-Sforza of Stanford University, have previously studied other types of DNA variants to trace populations. Founder mutations now add a new dimension to DNA studies: calibrating the haplotype length dates the mutation, and calculating the frequency of the haplotype in the population measures the geographic spread of the founders descendants.

Each of us bears biochemical witness to the fact that all humans are indeed members of a single family, bound together by the shared inheritance of our genome. In addition to confirming the Out of Africa hypothesis, analyses of founder mutations have revealed the common ancestry of various other seemingly unrelated groups--research by David B. Goldstein of Duke University, for instance, has revealed an unexpected genetic connection between the Celts and the Basques. Further investigations of founder mutations and their haplotypes will no doubt reveal more of the genetic relationships that give us new insights into where we came from and how we arrived at our modern locations. Such study also reveals surprising kinships that may inspire a deeper appreciation for the shared roots of humanitys family tree.

THE AUTHOR

DENNIS DRAYNA received his bachelors degree from the University of WisconsinMadison in 1975 and his Ph.D. from Harvard University in 1981. He did a postdoctoral fellowship at the Howard Hughes Medical Institute at the University of Utah and then spent 14 years in the biotechnology industry in the San Francisco Bay Area, where he identified a number of different human genes involved in cardiovascular and metabolic disorders. In 1996 he joined the National Institutes of Health, where he currently serves as a section chief in the National Institute on Deafness and Other Communication Disorders. His primary research interests are the genetics of human communication disorders, work that has taken him to eight different countries on four continents in pursuit of families with these disorders. In his spare time he enjoys technical rock and ice climbing in equally far-flung places.

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