A quick history of the church. The church that you see was built by Pope Leo II (681-83) who built it on the foundations of an earlier church. It was restored by Pope Gregory IV (827-44), but was subsequently damaged by heavy flooding in the area. (It is interesting how many churches suffered greatly from climate change in this time). Originally it was dedicated to both St George and St Sebastian, but in time the devotion to St Sebastian died out. The relic of St George was given to the church by Pope Zachary (741-52), who like St George was a native of Cappodocia. Presumably the relic was imported from his home town.
In the apse you can see St George, on a white horse to the right of Christ. This is the way that the Greek Church still depicts him. The suburb by the way was the centre of the Greek community as many refugees escaping iconoclast persecution in the eighth and ninth centuries settled in this neighbourhood. There is no reference to the dragon as this only turned up about 500 years after the church was built!