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In this question we are examining a bacterial RNA polymerase that elongates at 20 codons per second. Question 1: How long will this RNA polymerase take to transcribe the Lac Z gene at 3510 base pairs?

My answer: A codon is 3 base pairs so I start by dividing 3510 by 3 and then by 20 to get 58,5 seconds.

Question 2: Your bacteria can produce a Lac Z mRNA about every other second. How can you explain this?

My answer: I am very lost on this one. I thought that the mRNA would be as long as the gene so wouldn't this be 58,5 seconds not roughly 2 seconds??

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Multiple RNA Polymerase transcription complexes engaged on the lacZ gene at the same time, staggered along the gene.

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Either the gene is present in multiple copies (especially possible if it is in a plasmid) or multiple RNA polymerases are transcribing it, each beginning from the start site one after the other with some amount of time delay, much like multiple ribosomes translate the same mRNA to increase rate of protein production.

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