There are a lot of important ways to study the impact of the generations of trauma experienced by African Americans, but genetics is not one of them — the time scale for that is too short for genetics to play much of a role. Most of the DNA examined for the study in the article is “neutral”, meaning it has little if any effect on our biology, but it’s a useful marker for ancestry. Genetic variants related to disease are an exception — they’re not functionally neutral — but they’re not caused by trauma either; they’re simply inherited from our ancestors.

Understanding just how, as you say, generations of abuse has affected African Americans is absolutely an important subject, but genetics doesn’t have much more to say about it, other than to trace its impact on people’s genetic ancestry.