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 Answer 1


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.

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    $\begingroup$ 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, 2020 at 18:49

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