Why are there multiple sequences associated with a single transcript ID? Which sequences were the probes selected from?
For the HG-U133 design, multiple sequences may represent the same transcript if the transcript is alternatively polyadenylated (that is, there are short and long forms of the same transcript). The nucleotides may differ slightly among sequences sharing the same transcript ID. The specific sequence from which each probe is selected is annotated in the corresponding sequence record as "Used for Probe Selection: Yes".