Scientists have long been acutely interested in the genetic idiosyncrasies of Ashkenazi Jews. Like other groups with a long history of marrying from within, Ashkenazim constitute a relatively homogenous population.
This has led to the discovery of a number of genetic alterations, or mutations, that are responsible for diseases found more often in Ashkenazi Jews. Think Tay-Sachs, Gaucher’s or other so-called “Jewish genetic disorders.” But the smaller gene pool has also made it easier for scientists to find genes responsible for widespread ailments with complex genetic underpinnings, such as cancer and diabetes.
To date, such work has been done by looking at only a fraction of the genes in the entire human hereditary complement — usually just a million or so scattered DNA letters. But thanks to advances in gene sequencing technologies, and declining prices in their application, the pursuit of disease-causing mutations affecting Ashkenazim is about to advance by orders of magnitude — up to all 3 billion nucleotides that make up the human genome.
A group of leading researchers from across the United States and Israel is currently raising money to decode the genomes of more than 1,500 Ashkenazi Jews, including healthy individuals and those suffering from breast cancer, Crohn’s disease, schizophrenia and a handful of other common ailments. Most of these disorders in the academic hot seat are caused by multiple genes that, to date, have eluded scientific discovery.
It’s not that Ashkenazi Jews have more defective DNA or suffer such diseases at appreciably higher rates than other ethnic groups — they do not. Rather, because only a small number of ancestors from Central and Eastern Europe gave rise to the millions of Ashkenazim alive today, scientists like those involved in the nascent Ashkenazi Genome Project can compare healthy and sick Jews and, through statistical techniques, more easily pick out which genetic alterations might explain the medical discrepancies.
“With feasible investment and the sequencing of only hundreds of individuals, one can get very good representation of the genomes of millions of people living today,” says Itsik Pe’er, a computational biologist at Columbia University and one of the scientists who is spearheading the effort. “This is something that you cannot do in many other populations of interest to geneticists.”
Geneticists commonly study reproductively isolated populations. For example, the Old Order Amish and Hutterites are the subjects of active investigation in the United States, and many European island dwellers in Iceland, Sardinia and elsewhere have had their genomes decoded and analyzed. But these groups are relatively small — usually counted in the tens or hundreds of thousands. As a result, it can be hard for scientists — who need robust sample sizes to yield statistically meaningful results — to find sufficient numbers of study participants who suffer from any given disease.