Final answer:
During transcription, an RNA polymerase transcribes only one strand of one gene to produce an RNA molecule. In prokaryotes, a single type of RNA polymerase transcribes all genes, while eukaryotes have specialized RNA polymerases for different types of RNAs.
Step-by-step explanation:
Transcription Overview
During the process of transcription, one strand of a gene's DNA is used as a template to synthesize a complementary strand of RNA. The RNA polymerase enzyme is responsible for this process, and it transcribes only one strand of one gene at a time. This means that from the DNA's two strands, only the antisense (template) strand is used for transcription, not the whole chromosome or all chromosomes. The RNA molecule produced is a copy of the sense (coding) strand with uracil (U) replacing thymine (T). In bacteria, a single type of RNA polymerase transcribes all genes, whereas eukaryotes utilize different RNA polymerases for different types of genes.
Transcription in Prokaryotes and Eukaryotes
In prokaryotes, such as E. coli, the same RNA polymerase, associated with different sigma factors, is used for transcribing all types of RNA. By contrast, eukaryotes have three types of RNA polymerase depending on the RNA being transcribed: RNA polymerase II for protein-coding genes, RNA polymerase I for rRNA genes, and RNA polymerase III for tRNA and small nuclear RNA genes.
Transcription produces monocistronic mRNA in eukaryotes, which means each mRNA molecule encodes a single protein, as opposed to polycistronic mRNA in prokaryotes, which can encode multiple proteins.