en.wikipedia.org
Here's some very crude reading (wikipedia is a shit source) on the topic. Obviously, you can't get these conditions just by converting to Judaism. These are heritable. I can't really make this any more simple than this: a follower of Judaism is called a Jew, but the word Jew can also refer to member of a specific Semitic ethnic group. For instance, Karl Marx was an ethnic Jew, but not practicing. As someone else here posted, there are religious Jews, who are ethnically not Jewish.
Let's also ignore the rest of the post and dance around the point being made by pointing out me getting the year wrong.