What catalyzes the synthesis of mRNA?

RNA polymerase is the enzyme responsible for catalyzing the synthesis of messenger RNA (mRNA) during the process of transcription. Transcription is the first step of gene expression, where the information encoded in a DNA sequence is copied into mRNA so that it can then be translated into a protein.

During transcription, RNA polymerase binds to the DNA at a specific region known as the promoter. It then unwinds the DNA strands and begins synthesizing the complementary RNA strand by adding ribonucleotides that pair with the template DNA strand. This process continues until RNA polymerase reaches a termination signal, at which point the newly synthesized mRNA strand is released.

Ribosomes, while crucial for protein synthesis, function in translation and are not directly involved in the synthesis of mRNA. DNA polymerase, on the other hand, is involved in DNA replication, not RNA synthesis. Ligase is an enzyme that plays a role in joining DNA fragments together, particularly during DNA replication and repair, but does not catalyze the formation of RNA. Thus, RNA polymerase is the key enzyme that facilitates the transcription of DNA into mRNA, making it the correct answer for this question.