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BIOL 112 - Practice Qs from 2008

But the mutant protein may not be fully functional

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Unformatted text preview: g the protein. But the mutant protein may not be fully functional. Since lacI+ Permease is defective Lactose is nutrient For both the initiator protein and RNA polymerase to bind, the DNA sequences can’t overlap. If LacI had affinity for DNA in the presence of lactose, no transcription would occur because in the lac operon, the P and O do overlap. If LacI is bound, RNA polymerase is blocked from binding. This operon wouldn’t inhibit gene expression in response to an environmental signal, because transcription is only initiated in the presence of the signal, when the initiator protein and RNA polymerase bind. To ensure that the initiator protein is made, so that transcription of the operon would be possible, the initiator protein must be made all the time, but it doesn’t need to be transcribed in large amounts (see page 174), a few copies of the initiator protein would be sufficient....
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