By blood, Jewishness is only transferred through the mothers blood-line. One can choose to convert to Judaism but that doesn't count genetically.
We all come up short and therefore it is only by grace one can receive salvation through faith in Jesus Christ.
Well, Anon didn't make it up but if there is doubt; one can research for them self.
Traditional Jewish law (Halakha) dictates that Jewish status is passed down exclusively through the mother, meaning a person is automatically considered Jewish if their biological mother is Jewish.
However, looking at this through a modern lens requires separating traditional religious laws, modern denominational practices, and genetic science: