Assume that a bacterial cell produces a Lac repressor that is able to bind to the operator sequence of the lac operon but
cannot bind allolactose. Explain the effect on transcription of the lac operon is the presence and absence of lactose.
What will be an ideal response?
ANSWER: The Lac repressor binds the operator in the absence of lactose to prevent transcription of the
lac operon. However, when lactose is present, allolactose normally binds the repressor,
removing the repressor from the operator and allowing transcription to occur. In this mutant
bacterial cell, the repressor cannot bind allolactose. Therefore, there will be no transcription
even in the presence of lactose because the repressor will remain bound to the operator.
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a. 10?20 b. 20?30 c. 300?400 d. 4?7 e. 90?100
In this figure of teleost internal anatomy, which structure, A, B, C, or D, is the swim bladder?
1.A
2.B
3.C
4.D
During the Ames test, his? bacteria are exposed to a chemical. If the bacteria remains his+, then what can we say about the chemical?
A) The chemical is certainly a cancer-causing chemical. B) The chemical is not safe to consume because it is likely a mutagen. C) The chemical is safe to consume even though it is likely a mutagen. D) The chemical is safe to consume and is not likely a mutagen. E) The chemical is not safe to consume even though it is not likely a mutagen.
A molecule that binds to an enzyme at a location other than the active site and thereby alters the enzyme's shape, making it inactive or less active is a(n) ________ inhibitor.
Fill in the blank(s) with the appropriate word(s).