1. Imagine an operon that has three structural genes: Gene 1 makes Protein 1, Gene 2 makes Protein 2, and Gene 3 makes Protein 3. The genes are arranged physically in the operon in the order Gene 1, Gene 2, Gene 3, and transcribed in that order as well.
What would the effect be on production of Protein 3 if there was a missense mutation in Gene 1? Would you get the same effect on production of Protein 3 if there was a nonsense mutation in Gene 1? Explain your answer.
2. Please fill in the information in the table below, telling if an E. coli bacterium that has the following genotypes will make a functional form of beta-galactosidase and/or permease in the presence versus absence of lactose. If the bacterium will produce a functional version of the protein, indicate this with a plus sign ( "+" ). If it will not produce the protein, indicate this with a minus sign ("-"). Assume all mutations are missense mutations unless otherwise specified.
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Beta-gal
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Beta-gal
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Permease
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Permease
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Genotype
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Absence
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Presence
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Absence
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Presence
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lacI lacP+ lacO+ lacZ+ lacY+
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lacI+ lacP lacO+ lacZ+ lacY+
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lacI+ lacP+ lacO+ lacZ+ lacY+
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lacIs lacP+ lacO+ lacZ+ lacY+/ lacI+ lacP+ lacOc lacZ+ lacY+
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lacI lacP+ lacO+ lacZ+ lacY+/ lacI+ lacP+ lacOc lacZ+ lacY+
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lacI+ lacP lacO+ lacZ lacY+/ lacI+ lacP+ lacO+ lacZ+ lacY+
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lacI+ lacP lacO+ lacZ+ lacY+/ lacI+ lacP+ lacOc lacZ+ lacY+ ***
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lacI+ lacP lacO+ lacZ+ lacY+/ lacI+ lacP+ lacO+ lacZ lacY
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*** The Z mutation is a nonsense mutation.
3. Please explain how the presence or absence of tryptophan regulates the activity of the trp operon.
4. Please describe a mechanism whereby an interfering or antisense RNA can regulate production of a protein.