Founder Event Affects Genetic Variability In Ashkenazi Jewish Populations

Photo by Maayan Nemanov on Unsplash

Excavation of an old storehouse in efforts to build access ramps led to unearthing a medieval Jewish gravesite in Erfurt, Germany. From there, archaeologists were able to collect bags full of molars, bicuspids, and incisors from the bones of the dead buried there. Geneticists extracted DNA samples from 33 teeth. Studies of their DNA reveal how, despite being genetically related to the medieval Ashkenazi individuals of the Erfurt community, modern day Ashkenazim, even if they live worlds apart, have less genetic variation. From this study, scientists, geneticists, and researchers discovered the high level of homozygosity among modern Ashkenazi Jews around the world. The evidence suggests this was due to a bottleneck (founder) event where the original community experienced a reduction in population size and repopulated from the few that were left among them. 

It's inspiring to hear how DNA, whether it comes from a living person, or centuries old individual long buried, has a story, a history to share. The computational geneticist from Columbia University, Itsik Pe'er said it best, "Ancient DNA sequencing is a cheat-code that can take you to places where you don't have information today." 

South Asian Social Castes

An article in the New York Times discusses how recessive genes are very common in regional groups; this is due to the founders effect.  These recessive genes are expressed when the child receives the mutated gene from both parents which is much more common in regional groups since they participate in consanguineous mating.  The Vysva population has a gene mutation which causes a bad reaction to muscle relaxants, Ashkenzai Jews are susceptible to Gaucher disease and cystic fibrosis, and congenital nephrotic syndrome is prevalent in the Finns population.  The mutations range from not harmful to terminal which creates a higher than average mortality rate.  Recording data about these diseases is important because it allows for prenatal and premarital screenings.  These screenings have been used within the Ashkenazi Jew population and has basically eliminated new cases of Tay-sachs disease in the population.  These populations provide opportunities to study how genes manifest naturally in humans.  It is important to research even the rarest diseases because these mutations can be inherited even if you do not marry your first cousin, some bloodlines simply have a higher risk for certain mutations.