Draft sequence refers to DNA sequence that is not yet finished but is generally of high quality (i.e., an accuracy of greater than 90%). Draft sequence data are mostly in the form of 10,000 base pair-sized fragments, the approximate chromosomal locations of which are known. The following keywords are associated with draft sequence: phase 0, light-pass coverage of a clone, generally only 1× coverage; phase 1, 4–10× coverage of a BAC clone (order and orientation of the fragments are unknown); and phase 2, 4–10× coverage of a BAC clone (order and orientation of the fragments are known). Phase 3 refers to the completely finished sequence.