In transcription, RNA polymerase unwinds the DNA double helix and begins attaching RNA nucleotides to the template strand. In its wake, the DNA double helix closes back—this is only natural, seeing as the DNA bases have the tendency to hydrogen bond. In DNA replication, this closing is prevented by single-strand binding proteins.

I have three questions regarding this:

  1. In transcription, the pre-mRNA strand peels off the template strand in the wake of RNA polymerase. Why? There are just as well hydrogen bonds between the pre-mRNA strand and the DNA template strand as there are between the two DNA strands.
  2. Why doesn’t the pre-mRNA stick onto the DNA indefinitely and block the non-template DNA strand from reattaching to the template DNA strand?
  3. In DNA replication, why is it imperative that the separated DNA be stabilized by single-strand binding proteins? Won’t the replicated strand block the template strands from closing together?

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