Question

What happens when a hairpin loop forms in mRNA?

a.) The RNA polymerase and the mRNA dissociate from the DNA.
b.) Transcription of DNA to mRNA begins.
c.) Exons are removed from the RNA transcript.
d.) Transcription of the coding strand begins.

Answer 1

A hairpin loop in mRNA signals the end of transcription through Rho-independent termination. The stable hairpin causes RNA polymerase to stall and ultimately detach from the DNA template alongside the mRNA.

Step-by-step explanation:

When a hairpin loop forms in mRNA, it often signals the end of transcription. This loop occurs due to Rho-independent termination, a process that involves specific DNA sequences. As RNA polymerase transcribes the DNA into mRNA, it eventually reaches a sequence rich in C-G nucleotides. This causes the newly synthesized mRNA to fold back on itself, forming complementary C-G pairings which result in a stable hairpin structure.

This structure, in connection with a region rich in A-T nucleotides that are transcribed into weak U-A bonds with the template DNA, stalls the polymerase. Consequently, the instability caused by the weak U-A bonds and the stalled enzyme leads to the detachment of RNA polymerase along with the newly synthesized mRNA strand from the DNA template.