Which enzyme is responsible for catalyzing the transcription process?

RNA polymerase is the enzyme critical for catalyzing the transcription process, which is the first step in gene expression where a specific segment of DNA is copied into RNA. This enzyme binds to a promoter region on the DNA and unwinds the double helix, allowing it to read the template strand. As it moves along the DNA, RNA polymerase synthesizes a complementary RNA strand by incorporating RNA nucleotides that are complementary to the DNA template. This process continues until RNA polymerase reaches a termination signal in the DNA, where transcription is completed, and the newly synthesized RNA molecule is released.

In contrast, DNA polymerase is involved in DNA replication, constructing a new strand of DNA based on a DNA template. Ligase is responsible for joining Okazaki fragments on the lagging strand during DNA replication, and ribonuclease is involved in RNA processing and degradation rather than synthesis. Therefore, the specific role of RNA polymerase in transcription makes it the correct answer.