Human DNA Polymerase Alpha is a replication enzyme used to test the toxicity of drugs on key human replication systems. It is the replication enzyme involved in initiation of DNA replication in eukaryotes. In a complex with primase, Pol α synthesizes chimeric RNA-DNA primers necessary for replication of both chromosomal DNA strands. Pol α has limited processivity and lacks 3′ exonuclease activity for proofreading errors.