What is transcription and what enzyme catalyzes it?

Transcription is the process of synthesizing RNA from a DNA template, representing the first step in gene expression. RNA polymerase is the enzyme that catalyzes transcription by reading the template strand 3' to 5' and synthesizing RNA 5' to 3'. In prokaryotes, a single RNA polymerase handles all transcription, while eukaryotes have RNA Pol I (rRNA), RNA Pol II (mRNA), and RNA Pol III (tRNA and small RNAs). The process involves initiation at promoters, elongation, and termination.