In DNA, New Clues to Jewish Roots

"Dr. Schiffman said that as president of the Association for Jewish Studies he would consider convening a discussion between the geneticists and the historians on interpreting the new data. He noted that the study of racial differences had led to disaster in the past but that the new analysis of genetic differences was 'a form of racial science for the good, rather than the bad.'

'Racial science,' Dr. Schiffman said, 'has brought so many terrible things. But it's a norm now in genetics to study the racial genetics of groups. So I think it's an amazing difference.'

Geneticists use the Y chromosome and mitochondrial DNA to track the movement of populations because each is passed unchanged from parent to child, escaping the genetic shuffle that occurs on the rest of genome between generations. Since the Y chromosome passes down only from father to son, and mitochondrial DNA is always inherited from the mother alone, the two elements serve to track the genetic history of men and women respectively.

But since the Y chromosome and mitochondrial DNA clock up occasional changes or mutations every thousand years or so, on much the same time scale as human population splits, different ethnic groups tend to have characteristic patterns of mutations.
The Y chromosome and mitochondrial DNA's in today's Jewish communities reflect the ancestry of their male and female founders but say little about the rest of the genome, which is by now a presumably well mixed set of genes contributed by all the founders of each community.
Noting that the Y chromosome points to a Middle Eastern origin of Jewish communities and the mitochondrial DNA to a possibly local origin, Dr. Goldstein said that the composition of ordinary chromosomes, which carry most of the genes, was impossible to assess.
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