It helps thinking about it the other way around, ie. nationality has DNA. For Americans this may sound absurd, but it's very common in non-immigration heavy countries. Whether "German" or "Norwegian" are nationalities or ethnicities is not a settled debate. This is why being non-white in Europe can be hard in some ways. Some Germans have a rather uncharming word for people with their nationality but not their ethnicity: passport-German. The meaning being that you're not really German, you just have citizenship, which is far less meaningful. I'm not hating on the Germans, btw; most countries are worse than Germany. I chose it as an example because they debate a lot about this, so everything's really visible. Just know that the US is the exception.