Original: It was n't until 1944 that Griffith's "transforming principle" was identified as DNA by Oswald Theodore Avery, along with coworkers Colin MacLeod and Maclyn McCarty.
Simplified: Years later Griffith's "transforming principle" was identified as DNA by Oswald Theodore Avery, along with coworkers Colin MacLeod and Maclyn McCarty, in 1944.