A B737 CREW DEPARTING LAS TURNED EARLY ON THE IDALE 1 DEP INTO HIGHER TERRAIN.

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B737; ON IDALE 1 DEP (RNAV DEP) ON THE DEP TURNED 3-4 MI TOO EARLY; BEFORE IDALE; TURNED W INTO HIGHER TERRAIN. PLT TURNED EARLY WITHOUT ATC'S INSTRUCTION. PLTDEV SUPVR INFORMED. THIS OCCURRED WHILE WORKING W DEP AT XA27Z. I OBSERVED B737 AT ABOUT 8000 FT IN A 4500 FT MOA. SUPPLEMENTAL INFO FROM ACN 553775: AFTER ENG START AND TAXI; GND CTL ISSUED A RWY AND DEP ROUTING CHANGE; RWY 25R ON THE IDALE DEP. ORIGINAL RWY WAS RWY 7L ON THE MINEY DEP. FO REPROGRAMMED FMC DURING TAXI TO RWY 25R. THE DEP WAS NORMAL UNTIL THE IDALE FIX. WITH THE AUTOPLT ENGAGED AND THE LNAV MODE SELECTED; THE ACFT STARTED A R NORTHWESTERLY TURN. WE RECOGNIZED THAT SOMETHING WAS WRONG DUE TO OUR PROX TO HIGH TERRAIN. FMC ROUTING SHOWED THE NEXT FIX; COALDALE (OAK) AT 304 DEGS. AFTER TURNING 60 DEGS; DEP CTL ASKED 'ARE YOU TURNING? YOU TURNED 3 MI EARLY.' HE THEN GAVE US A TURN TO HDG 220 DEGS (TOWARD HIGH TERRAIN?) AND A CLB TO 11000 FT. WE STARTED THE TURN AND CLB AND ADVISED THAT 'WE HAVE THE TERRAIN IN SIGHT.' WE THEN DISCOVERED THAT 2 FIXES (SHEAD AND BIKKR) HAD BEEN DELETED FROM THE DEP ROUTING. WE WERE THEN CLRED TO SHEAD FIX WHICH WE HAD TO ENTER MANUALLY INTO THE FMC. CAUSE OF INCIDENT: FMC ROUTING ERROR. 2 FIXES DELETED/OMITTED FROM THE DEP ROUTING. CONTRIBUTING FACTORS: CHANGE OF RWY/DEP ROUTING WHILE TAXIING. LOCATION OF SINGLE FMC INSTALLATION IN COCKPIT REQUIRING XCOCKPIT SCAN WHILE TAXIING AND FLYING.