In trying to distinguish between the two models of eukaryotic transcriptional termination,you identify a drug that specifically blocks exonuclease activity.When you add it at the appropriate time to an in vitro system that carries out all the stages of eukaryotic transcription,you find that transcription proceeds normally,but transcription doesn't terminate. This experiment provides support for which model of eukaryotic transcriptional termination?
A) Allosteric model
B) Torpedo model
C) Rho-dependent termination
D) Rho-independent termination

Question

In trying to distinguish between the two models of eukaryotic transcriptional termination,you identify a drug that specifically blocks exonuclease activity.When you add it at the appropriate time to an in vitro system that carries out all the stages of eukaryotic transcription,you find that transcription proceeds normally,but transcription doesn't terminate. This experiment provides support for which model of eukaryotic transcriptional termination?
A) Allosteric model
B) Torpedo model
C) Rho-dependent termination
D) Rho-independent termination

Quizplus · Accepted Answer

The fact that transcription proceeds normally but doesn't terminate when exonuclease activity is blocked indicates that the 5' end of the mRNA is not being cleaved, and thus the "torpedo" RNA transcript is not being generated to trigger termination. This supports the torpedo model of eukaryotic transcriptional termination. The allosteric model involves a change in the polymerase itself triggering termination, and rho-dependent and rho-independent termination involve the use of the protein rho to cause termination. None of these models are directly related to the presence or absence of exonuclease activity.

In Trying to Distinguish Between the Two Models of Eukaryotic