Is it true prisons are filled with men with extra male chromosome?

No.: Older studies suggested an association between 47xyy and aggression/incarceration. In fact, these studies were methodologically flawed and this is not true. Newer studies have proven that affected individuals are slightly intellectually challenged (drop of IQ by 10 points) and thus are more likely to get into trouble with the law for minor offenses due to poor judgment (not aggression).