5' RACE and 3' RACE PCR is a method used to identify the full sequence of a mRNA strand, primed with specific primers to known partial sequences. The sequence within could contain a gene of interest, which may help in efforts to clone and express them in a host organism.
to determine the 5' and 3' ends of a mRNA without knowing a place to have a primer anneal to in that region. In particular was useful for rare mRNAs as it allows multiple round of amplification and nesting using the homopolymer tail.