Complex sentence: The study's major findings were that the Y chromosome of the Jefferson family matched that of Eston Hemings's family, while the Y chromosomes of the Woodson and Carr families differed from that of the Jefferson family.
Split into simpler sentences: The study's major findings were that the Y chromosome of the Jefferson family matched that of Eston Hemings's descendants. The Y chromosomes of the Woodson and Carr families differed from that of the Jefferson family.