Because certain very specific subgroups have done this doesn't mean that they are "pure". These in-marrying groups are always descended from mixed populations in the first place, populations that predate the identity badges we ascribe to them today.
Tay Sachs, among the genetic diseases you alluded to, is also present in non Jewish populations, but at a lower rate:
https://www.haaretz.com/jewish/non-jews-increasingly-hit-by-...
> I don't know the specifics, but I've read that only certified Jews can officially marry in Israel. > And the standards are so high that many "Jewish" immigrants don't qualify.
People can convert to Judaism, and even be born into Judaism with one Jewish parent. This is very common among populations outside of Israel.
Large subgroups in Judaism, sephardi, baghdadi, etc, are genetically quite diverse in origin, and are significantly represented among the Israeli population.
Yes, but to strict orthodox, they're not really "Jewish".
At one point, I researched rabbinical criteria for determining pedigree and classifying degree of Jewishness. Who can marry who, and how any children are classified. It's mind-boggling. If I have some time while this thread is hot, I'll post some sources.
Edit: Here are some sources. Please note that they're Jewish sources. Not anti-Jewish sources.
http://www.jewishencyclopedia.com/articles/11977-pedigree
https://www.chabad.org/library/article_cdo/aid/4045946/jewis...
https://tikvahfund.org/uncategorized/intermarriage-can-anyth...
https://www.jewishvirtuallibrary.org/marriage-in-judaism
http://www.cohen-levi.org/jewish_genes_and_genealogy/the_dna...
Unless you are seeking to identify as "strict orthodox", why would it matter?
The majority of Jewish groups are welcoming to people from the outside, if they achieve the required objectives in terms of religious and cultural fluency.
I don't know the specifics, but I've read that only certified Jews can officially marry in Israel. And the standards are so high that many "Jewish" immigrants don't qualify.
Now that we have DNA testing, I wonder if that will become the standard.