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Kaplan Qbank USMLE



Author3 Posts
  #1

Can anyone explain to me in histidine operon why transcription terminated when ribosome is able to slide fast on mRNA? :roll: Thanks.

  #2

The main essence behind this HISTIDINE operon Attenuation is:
Transcription/Translation proceeds in the low level of Histidine in the medium.
Transcription termintes soon in the presence of high level of Histidine in the medium, the logic behind is, there is no need to transcribe and translate amino acid (Histidine) biosynthesis when there is already enough histidine in the medium. think of it as a NEGATIVE FEEDBACK.
Because of the easy availability of Histidines from the medium, ribosome can speedily get hold of Histidine from the medium and attach it to the codons when translating. because of this speed it forms a stem and loop with poly u tail which basically works as a terminator. it is a sort of regulatory mechanism.
I hope this makes sense.


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  #3

http://web.mit.edu/esgbio/www/pge/pgeother.html

this website explains about the attenuation of histidine operon pretty well...


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