The Fund seeks to track the investment results of the Bloomberg U.S. GNMA Bond Index. The Fund will invest at least 80% of its assets in the component securities of the Underlying Index and to-be-announced transactions (TBAs) that have economic characteristics that are substantially identical to the economic characteristics of the component securities of the Underlying Index, and the Fund will invest at least 90% of its assets in fixed income securities of the types included in the Underlying Index that BFA believes will help the Fund track the Underlying Index.