<P> PCR usually generates blunt - ended PCR products, but note that PCR using Taq polymerase can add an extra adenine (A) to the 3' end of the PCR product . This property may be exploited in TA cloning where the ends of the PCR product can anneal to the T end of a vector . TA ligation is therefore a form of sticky end ligation . Blunt - ended vectors may be turned into vector for TA ligation with dideoxythymidine triphosphate (ddTTP) using terminal transferase . </P> <P> For the cloning of an insert into a circular plasmid: </P> <Ul> <Li> The total DNA concentration used should be less than 10 μg / ml as the plasmid needs to recircularize . </Li> <Li> The molar ratio of insert to vector is usually used at around 3: 1 . Very high ratio may produce multiple inserts . The ratio may be adjusted depending on the size of the insert, and other ratios may be used, such as 1: 1 . </Li> </Ul> <Li> The total DNA concentration used should be less than 10 μg / ml as the plasmid needs to recircularize . </Li>

Function of atp in dna ligation mediated by t4 dna ligase