What are similarities and differences among the transcription process and the replication processes?

A DNA polynucleotide chain serves as a template in replication (DNA duplication) as well as in transcription (RNA formation). In both processes the pairing of the two polynucleotide chains of the original DNA molecule is broken by the breaking of hydrogen bonds for the chains to be exposed as templates. The reaction is catalyzed by exact enzymes in transcription and in replication.

In replication the enzyme DNA polymerase catalyzes the formation of a new polynucleotide chain using free nucleotides in solution and putting them in the new chain according to the DNA template exposed and to the rule A-T, C-G. In transcription the enzyme RNA polymerase makes a new polynucletide chain according to the DNA template exposed obeying, though, the rule A-U, C-G.

In replication the original template DNA chain is kept bound by hydrogen bonds to the newly produced DNA chain and a new DNA molecule is then formed. In transcription the association among the template DNA chain and the newly formed RNA is undone and RNA constituted of only one polynucleotide chain is liberated.