Lac and Trp Operon

Reformat to indicate that answer completes stem: "If glucose is absent but lactose is present, the lac operon will be____________."

• activated

• repressed

• partially activated

• mutated

What would happen if the operator sequence of the lac operon contained a mutation that prevented the repressor protein from binding the operator?

• In the presence of lactose, the lac operon will not be transcribed.

• In the absence of lactose, the lac operon will be transcribed.

• The cAMP-CAP complex will not increase RNA synthesis.

• The RNA polymerase will not bind the promoter.

What would happen if the operator sequence of the trp operon contained a mutation that prevented the repressor protein from binding to the operator?

• In the absence of tryptophan, the genes trpA-E will not be transcribed.

• In the absence of tryptophan, only genes trpE and trpD will be transcribed.

• In the presence of tryptophan, the genes trpA-E will be transcribed.

• In the presence of tryptophan, the trpE gene will not be transcribed.

Tags

NGSS.HS-LS3-2

Repressor of lac operon can be bound by _____________________ which induces changes in its __________________  and repressor is no longer able to inhibit the lac operon transcription. 2p

What happens with trp operon transcription when there is a high concentration of tryptophan and E.coli does not need to synthesis it anymore? Explain inhibiting system using corepressor and repressor of trp operon.4p

1.     What does a corepressor do? 1p

Which of these operons is anabolic?

• Lac

• Ara

• Trp

• Phe

Which of these systems give the best mode for turning trp operon off?

• Repressor

• Attenuator

• Repressor with a downstream poly A tail

• Repressor with an attenuator

A Lac repressor is a tetramer repressed when bound to the inducer. The trp repressor is a ____________________

• Dimer inactivated when bound to the inducer

• Dimer activated on inducer binding

• Tetramer inactivated on inducer binding

• Tetramer activated on inducer binding

We know that lactose has a positive impact on the activity of the lac operon. Tryptophan’s presence has a ________________

• Positive feedback

• Negative feedback

• No difference

• Highly positive impact