Questions on Jewish Lineage

Question 1: If a DNA test shows Ashkenazi Jewish ancestry through the mother's side, does this automatically make someone Jewish in Modern Orthodox Judaism? What genetic percentage matters, and how can maternal Jewish status be definitively proven beyond verbal claims? Question 2: In determining a child's Jewish status through the mother, is it the mother's egg or the womb that matters? If a Jewish woman's egg is implanted in a non-Jewish surrogate, would the child still be considered Jewish?

Shalom!

Thank you for your question.

Regarding Question #1:

As a general rule, DNA evidence is inadmissible eon its own in Jewish law, especially when determining Jewish status. Nevertheless, sometimes it is accepted when other factors and considerations support it, as well. The bottom line, however, is that one whose mother is Jewish, is also Jewish. One whose mother is not Jewish, is not Jewish even if the father is Jewish. Therefore, one who can trace one’s lineage back through Jewish women, one after the other, is Jewish no matter what religion these people did or did not practice. That's all that halacha cares about. If the tradition has been lost, then DNA alone will not establish someone as Jewish. Conversion will also always be needed if the tradition has been lost. Your local orthodox rabbi should be able to help you with this.

Regarding Question #2

If a Jewish woman's egg is implanted in a non-Jewish surrogate then the child would need “giyur l’chumra” a conversion due to the doubt.