Help! DNA ethnicity test - how does it work?

[Clawdy]

Just got my Ancestry dna ethnicity results back - pretty much as I guessed , mainly English, but one thing is puzzling me. I was always told my great-grandad was Jewish. My results show 1% Basque ancestry which I'm guessing links maybe to a Sephardic ancestor, but certainly not a great-grandad, who would be nearer 10%. Could it be that his family had lived in England for generations back, and that would show as English? Or wouldn't it? Is that how it works?

It means that 1% of your dna is common to that seen in the Basque Country
If your results are mainly English, I’d assume your great grandfather was English too with lots of English ancestry

It just seems odd that we were told that about the great-grandad. I just wondered if it's more about where you have lived.

Is it possible he was English and converted? What were your other results? Could he have been Ashkenazi?

Other results were mainly English, Irish and a bit of Welsh! The family story was that my Irish great-gran met an Orthodox Jewish man, they fell in love, had children but never married. His family cut him off completely, and when I tried to do online research I can't find anything about him. So I'm wondering now if it was a strange family tale that isn't true. Our surname sounds Jewish, but could also be English! My father had black hair and dark eyes, and everyone assumed he was "foreign"! Guess I'll never know, as everyone is dead now, except me and my sister.