Duplication of DNA molecule is known as replication. The DNA is copied by enzymes called DNA polymerases which act on single stranded DNA synthesizing a new strand complementary to the original strand. DNA polymerases require a short double stranded region to initiate or prime DNA synthesis, this is produced by an RNA polymerase, called primase, which is able to initiate synthesis on single stranded DNA. The final step required to complete synthesis of the lagging strand is for the Okazaki fragments to be joined together by phosphodiester bonds which is carried out by a DNA ligase.