Question

An exonuclease binds to the 5'-end of the RNA that is being transcribed and degrades it in the 5' to 3' direction. The exonuclease then catches up to RNA polymerase II and causes termination. This describes the ______model of transcription termination in eukaryotes.

Answer 1

The student's question describes the torpedo model, which is a method of transcription termination specific to RNA polymerase II in eukaryotes.

Step-by-step explanation:

The student is referring to a specific model of transcription termination in eukaryotes known as the torpedo model. Unlike RNA polymerase I and RNA polymerase III, which require specific termination signals, RNA polymerase II transcribes several thousand nucleotides past the actual end of the gene. The excess RNA is removed during pre-mRNA processing. In eukaryotic RNA processing, a 5'-cap and a poly-A tail are added to protect the mRNA from degradation by exonucleases.