I read somewhere that every Jew now living, is a descendant of Judah, the son of Jacob (in Genesis). Is that true?
Well, there is a famous genetic marker, the “Cohen” sequence, that is used to identify people and groups around the world who descend from Israel, and that sequence actually comes from the tribe of Levi. The majority of the surviving Jews probably do descend mainly from Judah, but there were survivors from all 12 tribes that formed the population we identify as “Jewish” today.