Pinkginxx
Go back a few hundred years. Jewish people originated in and around what is now Israel.
Say 1000 people left, they all have Jewish/Israeli DNA, they go to live in 4 different places so 250 in each area. The 250 who go to Eastern Europe live amongst people with European DNA but marry within the 250 people. Judaism doesn't actively go out to convert people so grand children and great grandchildren share their DNA with their own community and with the descendents of the other 750 in different places.
Then there are two things that can happen, one is a mutation in the genes, so if this is the group of Jews living in eastern Europe they now share most of their DNA with the other 750 but there is a mutation that means there is a small difference.
The second thing is that although conversion to Judaism isn't common it does happen and the most common reason will be a marriage between one of the 250 and their descendents and a local.
This introduces a new gene in to the gene pool of the group in Europe.
Now the same things will be happening in the other groups,so they are developing small changes too.
Now if someone leaves one of the groups and travels to, say Scotland, they take their 'Jewish eastern European DNA' with them.
They may not practice their faith, or even totally leave it. If they then marry a local Scottish girl then their child will have a mix of Scottish and Jewish (E European) ancestry.
That person's children, grandchildren etc will have that DNA which will be mixed with the DNA of the other parent.