Question31 Which of these are constitutive mutants of the lac system and as such would cause the constant expression of the Z, Y, and A genes associated with the lac operon? Select up to two alternatives: Oc Y+ I− Z+ ResetMaximum marks: 1 Unflag question undefined

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Question31 Which of these are constitutive mutants of the lac system and as such would cause the constant expression of the Z, Y, and A genes associated with the lac operon? Select up to two alternatives: Oc Y+ I− Z+ ResetMaximum marks: 1 Unflag question undefined

BlackTom AI · Accepted Answer

The question asks which mutations would lead to constitutive expression of the lac operon genes Z, Y, and A, meaning continuous expression regardless of lactose presence.
Option Oc: The Oc mutation is in the operator sequence itself, preventing the repressor from binding. With the operator unreceptive to repression, RNA polymerase can proceed with transcription continuously, causing constitutive expression of Z, Y, and A. This makes Oc a classic constitutive operator mutant.
Option Y+: The Y+ allele is the wild-type (normal) version of the lacZ gene. By itself, Y+ does not cause constitutive expression; it simply encodes functional beta-galactosidase when the operon is active. Therefore, Y+ does not produce constitutive expression.
Option I−: The I− allele denotes a repressor that cannot bind to the operator. If the repressor cannot bind, repression is lost and the operon is expressed continuously, leading to constitutive expression of Z, Y, and A. Thus I− functions as a constitutive mutant.
Option Z+: Similar to Y+, Z+ is the wild-type form of the lacZ gene. Alone, it does not cause constitutive expression; it will be expressed only when the operon is active. Therefore, Z+ does not yield constitutive expression.
In summary, the mutations that remove repression or prevent operator binding (Oc and I−) explain constitutive expression, while the wild-type alleles (Y+ and Z+) do not by themselves drive constant expression.

Question31 Which of these are constitutive mutants of the lac system and as such would cause the constant expression of the Z, Y, and A genes associated with the lac operon? Select up to two alternatives: Oc Y+ I− Z+ ResetMaximum marks: 1 Unflag question undefined

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类似问题

When glucose is present, and lactose is absent in the bacteria cell’s environment, which of the following is INCORRECT with respect to the lac operon?

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Question at position 7 Cells of which bacterial genotype would be able to utilize lactose as an energy source?I+O+Z+Y- /F’ (ISO+Z-Y+)ISO+Z+Y+I+O+Z-Y+I+OCZ+Y- /F’ (I+O+Z-Y+)Clear my selection

Bacteria require both lactose and glucose to be present to synthesise protein linked to a lac operon.

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