E. coli is widely used in laboratories to produce proteins from other organisms.
ID: 6560 • Letter: E
Question
E. coli is widely used in laboratories to produce proteins from other organisms.a. You have isolated a yeast gene that encodes a metabolic enzyme and you want to produce this enzyme in E. coli. You suspect that the yeast promoter will not work in E. coli. Why?
b. After replacing the yeast promoter with an E. coli promoter, you are pleased to detect RNA from the yeast gene but are confused because the RNA is almost twice the length of the mRNA from this gene isolated from yeast. Explain why this result might have occurred.
Explanation / Answer
A. Eukaryotic promoters bind to several different transcription factors, which attract the RNA polymerase complex. Prokaryotic promoters bind to sigma factors, which attract the RNA polymerase complex. The sites for these factors differ, so the eukaryotic promoter would not attract the prokaryotic sigma factors. B. If it magically does transcribe the gene, it still won't work. Eukaryotic genes contain introns, 'junk' DNA excised during eukaryotic transcription. Prokaryotic genes DON'T have introns, so they transcribe the 'good' DNA with the 'junk' DNA.
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