WAKE TURB EVENT OCCURRED DURING DSCNT INTO ORD BTWN A B737 FOLLOWING A B747 7 MI IN TRAIL; BOTH AT 250 KTS.

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INBOUND TO ORD ON OKK 1 ARR; ORD APCH ADVISED US THAT WE WERE IN TRAIL OF A B747. APCHING THE BEARZ INTXN ON A DSCNT CLRNC TO 11000 FT; WE ENCOUNTERED WAKE TURB WHILE PASSING THROUGH 12000 FT. BOTH ACFT WERE ASSIGNED AIRSPD OF 250 KTS FROM ATC. B747 WAS APPROX 7 NM AHEAD DSNDING THROUGH 11800 FT. FO WAS PF WITH AUTOPLT 'B' ENGAGED. FIRST WE OBSERVED THE YOKE CORRECTING WITH NEARLY FULL R AILERON; FOLLOWED BY ACFT BEGINNING A SMOOTH BUT RAPID ROLL TO THE L. FO DISENGAGED AUTOPLT AND BEGAN UPSET RECOVERY TECHNIQUE WITH COORDINATED R AILERON AND RUDDER. MAX ROLL TO L WAS OBSERVED BTWN 35-40 DEGS. ALL PAX WERE IN THEIR SEATS AT TIME AS SEATBELT SIGN WAS ON. THE 3 WORKING FLT ATTENDANTS WERE STANDING DURING EVENT. PURSER WAS ABLE TO STAY UPRIGHT AND MENTIONED SOME BRUISING. BOTH FLT ATTENDANTS IN AFT CABIN 'FLOATED MOMENTARILY' AND WERE UNABLE TO REMAIN UPRIGHT. THEY ALSO FELT THEY RECEIVED BRUISING ONLY. UPON ADVISING ATC OF EVENT; WE WERE GIVEN ALTS ABOVE THE B747 FOR REMAINDER OF APCH AND LNDG. ALL 3 FLT ATTENDANTS WERE ABLE TO CONTINUE ON WITH THE REST OF THEIR SCHEDULE WITH NO OBSERVED INJURIES.