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earenas1 earenas1
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Posts: 3
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7 years ago
Hello, I have answered these questions, this is my third attempt and have gotten several wrong. for each question there can be one or more than one correct answer.

1.
The transcription of the trp operon genes (genes for enzymes necessary to synthesize the amino acid tryptophan)
Question 1 options:

   includes a repressor that is activated when lactose binds.
   is default "on" but can be slowed by a repressor.
   is regulated by a repressor, which is made constitutively, but in an inactive form.
   as the levels of tryptophan rise in the cell, it (tryptophan) increasingly activates the repressor, which in turn blocks the transcription of the trp genes Rightwards Arrow decrease in the production of tryptophan.

2.
The figure above (from the Supplemental Reading) shows two basic ways that cells can regulate the concentration of a particular protein end product: 1) the cell can regulate whether or not enzymes in a pathway are active (through allosteric inhibition, shown with the top red arrow) or 2) they can regulate whether or not the enzymes are even made--by regulating transcription. Both process are controlled by the concentratrion of the end product. Which of the following statements is correct about this topic?

Question 2 options:
   In end product inhibition, the concentrations of all the enzymes drops.
   
In end product inhibition, as concentrations of the end product rise, less and less Precursor is converted to product A in the pathway.This means that as product rises in concentration, the pathway that leads to synthesis of the product is slowed

   
In end product inhibition, the end product binds to an allosteric site on Enzyme 1, which changes the shape of the enzyme such that it no longer does its job.

   
Cells can regulate the concentrations of enzymes by regulating whether or not the enzymes are made--regulation of transcription.

3.
Several important terms were introduced in the Supplemental Reading on operons. Which of the following correctly defines one of these terms?

Question 3 options:
   
Enzyme production is said to be "repressible" if its default is to be "off" but which can be stimulated by an inducer (such as the trp operon enzymes).

   
A protein is said to be "inducible" if its production default is to be "on" but whose gene expression can be repressed by a repressor molecule (such as the trp operon enzymes).

   
"Constitutive" genes are transcribed at a constant rate in cells-- genes for enzymes that are made all the time.

4.
Prokaryotes can conserve energy and resources by making proteins only when they need them. The ways in which a bacterium can block the production of a protein include

Question 4 options:
   blocking transcription of the gene that codes for the protein.
   preventing a ribosome from binding to the mRNA for that protein.
   
inhibiting the function of the protein after it is made.

   synthesizing the mRNA for that protein.

5.
The structure of the lac operon includes
Question 5 options:
   a segment of DNA called the promoter, to which a repressor protein can bind.
   a regulatory gene that codes for a repressor protein, and its promoter.
   several structural genes that all transcribed together into an mRNA.
   a segment of DNA called the operator, to which RNA pol binds.
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