DNA study reveals that the English are 'one-third' Anglo-Saxon - Medievalists.net:
Historians have long debated how extensive was the Anglo-Saxon settlement of Britain, which took place between the mid-fifth and early-seventh centuries. It was during this period that several Germanic peoples arrived and colonized parts of the England, but it was unknown how large this migration was and whether or not they mixed with the native population.
An opportunity to resolve these issues emerged with the discovery and excavation of three sites near Cambridge - five samples from Hinxton, four from Oakington and one from Linton. The Linton sample and two Hinxton samples are from the late Iron Age (~100 BCE), the four samples from Oakington from the early Anglo-Saxon period (fifth to sixth century), and three Hinxton samples from the middle Anglo-Saxon period (seventh to ninth century). The two Iron Age samples from Hinxton were male, while all other samples were female.