<P> DNA ligase is a specific type of enzyme , a ligase , ( EC 6.5. 1.1 ) that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond . It plays a role in repairing single - strand breaks in duplex DNA in living organisms , but some forms ( such as DNA ligase IV ) may specifically repair double - strand breaks ( i.e. a break in both complementary strands of DNA ) . Single - strand breaks are repaired by DNA ligase using the complementary strand of the double helix as a template , with DNA ligase creating the final phosphodiester bond to fully repair the DNA . </P>
which class of the enzymes can be used to join two fragments of dna
DNA ligase