For many years I have believed, based on stories I was told from an early age, that my grandparents on my mother’s side were Dutch Sefardi Jews. They were definitely Dutch, my grandfather Joel Kops went from Holland to England in the early 20th century and every evening he listened to the news from Hilversum in Dutch. They were very assimilated, with essentially no Jewish practices, but they were definitely Jews (all of my grandfather’s family remaining in Holland – 51 people – were murdered by the Nazis).
In order to find out if the story of my Sefardi origin was true I had a genealogist trace my family back 4 generations, but all the surnames she uncovered were Ashkenazi names. I also discovered that although ca. 5,000 Sefardi Jews moved to Holland from Spain after the expulsion of 1492 (Holland had been a Spanish colony and was very anti-Spanish and anti-Catholic), also soon after another 5,000 Ashkenazi Jews also moved to Holland. So it was a toss-up. Then I decided to do the acid test, a DNA test.
Without going into the details, one can analyze the sequence of bases in the DNA taken from almost any cells in the body (usually the oral mucosa), and compare the analysis to many others from different ethnic groups. They can analyze the Y-chromosome to trace the patrilineal descent and the mitochondrial (mt)-DNA to trace the matrilineal descent, as well as the total DNA (genome) content. The company called Family Tree DNA (see http://www.familytreedna.com ) has built up a large data base of such characteristic ethnic DNA sequences, particularly with a large Jewish database, and by statistical comparison they can tell you your individual ethnic background. The tests cost several hundred dollars.
My results were that I am 89% Ashkenazi Jewish and only 6% Sefardi, with 3% West Middle East and 2% south-east Europe (Italy-Greece). Given that my father’s family were Ashkenazi Jews from the Ukraine, assuming they had no Sefardi origins, this means that my Sefardi origin on my mother’s side was ca. 12%, certainly less than the 50% that I was expecting. So the story of my Sefardi origins was perhaps somewhat exaggerated, but nevertheless is real.