Final answer:
In prokaryotic cells, transcription stops and the mRNA molecule is released after encountering specific signals in DNA: Rho-dependent or Rho-independent termination. Rho-dependent termination involves the rho protein causing the release of mRNA, while Rho-independent termination is mediated by a hairpin structure formed in the mRNA.
Step-by-step explanation:
Transcription Termination in Prokaryotes
Similar signals in DNA cause transcription to stop when a new mRNA molecule is completed. In prokaryotes, there are two types of termination signals for transcription: Rho-dependent termination and Rho-independent termination. The Rho-dependent mechanism involves the rho protein, which follows the RNA polymerase and prompts the release of the mRNA when the polymerase stalls at a run of G nucleotides.
On the other hand, the Rho-independent mechanism relies on the formation of a hairpin structure in the mRNA which leads to the stalling of the RNA polymerase and the subsequent release of the mRNA molecule.
Rho-independent termination involves a sequence in the DNA that is rich in C-G nucleotides, causing the mRNA to fold onto itself and form a stable hairpin. This structure, combined with a weak interaction of the U-A mRNA region with the template DNA, leads to the disassociation of the RNA polymerase from the DNA and the liberation of the newly synthesized mRNA.