Final answer:
RI terminators are specific DNA sequences that trigger rho-independent termination of transcription by forming a stable hairpin loop in the mRNA, resulting in the stalling and dissociation of RNA polymerase and the release of the mRNA transcript.
Step-by-step explanation:
The characteristic of RI terminators in a DNA sequence relates to the mechanism of rho-independent termination of transcription in prokaryotes. This termination process is guided by specific sequences within the DNA that cause the RNA polymerase to stall and dissociate, thus releasing the newly synthesized mRNA. When RNA polymerase transcribes DNA and nears the end of a gene, it encounters a sequence rich in C-G nucleotides. This induces the formation of a hairpin loop in the RNA because these nucleotides can bind to each other. This loop is followed by a region rich in A-T nucleotides, which when transcribed into RNA, forms a sequence rich in A-U pairs. These pairs only weakly bind to the DNA, leading to instability. This coupled effect of the stable hairpin and the weak A-U interactions cause the polymerase to stall and subsequently break away, freeing the mRNA to be used in protein synthesis.