mike650

hi i've been fixing up my 650 dragstar over winter it looks amazing now. when i came to start it the battery was dead so i decided to jump start it from my car, i've done this befor with no problems' i asked my brother to conect the cable to the bike and i did the car, nothing happend the bike didnt start. when i looked at it my bro had conected the negative to the posative and vice verca. i no this is a seriouse problem as the bike is completly dead now,i was woundering if some one could give me a list of things that could of brokern or any sujestions on what to do thanks.