I was learning about transcription factors and RNA polymerase from Khan Academy to supplement Dr. Robert Sapolsky's lectures on Human Behavioral Biology. As I understand:

  • RNA Polymerase transcribes DNA to RNA
  • Transcription factors are proteins that help the RNA Polymerase bind or inhibit it from binding to the DNA and transcribe it to RNA
  • Transcription factors called activators help RNA Polymerase bind to the DNA
  • Transcription factors called repressors prevent RNA Polymerase from binding to the DNA

It seems like we need transcription factors and RNA Polymerase to express genes and produce their corresponding proteins. But transcription factors and RNA Polymerase are proteins themselves. Thus, they must have come from their own respective genes. This seems like a "chicken and egg" problem.

How did early organisms with genetic material get around this problem?

  • 1
    $\begingroup$ You might look into the transition between the RNA and DNA world: ncbi.nlm.nih.gov/books/NBK6360 $\endgroup$ – Alex Reynolds Jun 16 '20 at 6:53
  • $\begingroup$ Isnt' it indeed some "chicken and egg" problem - solved, as the egg transfers existing protein from the mother that has not to be made from nothing (without any inheritance of template)? $\endgroup$ – Peter Bernhard Jan 1 at 12:12

This is one of the main features of the RNA World. What I mean by that is, RNA not only acts as a repository of genetic information, it also acts as an enzyme. This enzyme is known as Ribozyme. Ribozyme confers a self-replicating property to RNA, leading to the hypothesis that RNA might be the ancestor to the present day self-replicating genetic material.

  • 2
    $\begingroup$ The word ribozyme just means “RNA enzyme”. It does not define the catalytic function of the RNA. You are correct in implying that the RNA world hypothesis suggests that an RNA ur-genome might have been able to replicate itself without a protein RNA polymerase. However I am not aware of any contemporary ribozyme with this ability. Are you? Most seem to be nucleases or RNA ligases. $\endgroup$ – David Jul 18 '20 at 18:49
  • $\begingroup$ @David Very useful comment, that sums up, too. You mention "RNA ligases" - isn't there some theory about "the beginning" that states RNA being added as complements to an existing RNA-template? It should be fairly easy to "ligate" those added complements, thus making it appear more complex to synthesize the RNA as such from the dirt and clay and concentrate it close to the template. $\endgroup$ – Peter Bernhard Jan 1 at 12:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.