A sequence of RNA is synthesized on the template, so that the free 3’–OH end of the RNA chain is extended by DNA Pol and This is commonly used in replication of cellular DNA and by some viruses.
In case of reteroviruses, A preformed RNA (often a tRNA) pairs with the template, allowing its 3’–OH end to be used to prime DNA synthesis.
#Unit 3. Fundamental Processes#Mechanism of DNA synthesis in Prokaryotes#Part B Pointers
