partial RNA sequence identification primer extension assay ppm Primer extension can be used to determine the 3' end of a given sequence of RNA. This technique requires a radiolabelled primer which is complementary to a region near the 3' end of the RNA. The primer is allowed to anneal to the RNA and reverse transcriptase is used to synthesize a strand of DNA from the RNA until it reaches the 5' end of the RNA. By denaturing the hybrid and using the extended primer DNA strand as a marker on an electrophoretic gel, it is possible to determine the transcriptional start site. 2015-08-11T17:22:38Z MI:2203 PSI-MI primer extension assay