Geraldo isolated an E. coli strain in which a mutation has hampered the capacity of the cAMP activator to bind the promoter of the lactose operon. How will this mutation affect transcription of the lactose operon when the E. coli cells are exposed to the following conditions?
a. Lactose and glucose are both available.
b. Lactose is available but glucose is not.
c. Both lactose and glucose are absent.
The mutation in an E. coli strain has hampered the capacity of CAP protein to bind near the promoter region of the lac operon. This in turn means that the RNA polymerase necessary for the transcription of the genes for lactose-metabolizing enzymes cannot bind. Lactose will therefore not be metabolized if it is present.
(a) If both lactose and glucose are present, the bacteria will metabolize the glucose by preference due to the non-binding mentioned just above.
(b) If lactose is available but not glucose, normally the lactose-metabolizing enzymes would kick in, but they are not available due to the non-binding. In this case, the bacterium has an energy source, but it is not usable.
(c) If both lactose and glucose are absent, the bacterium has no energy source, unless the pathway for another sugar is somehow induced.
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You modify the primary sequence of an enzyme in a region that will be the active site when the protein is properly
folded. What is the predicted outcome of this change?
a. The enzyme will not bind to the substrate properly. b. The enzyme will not be able to bind an allosteric inhibitor. c. The enzyme will have an increased rate of activity. d. There will be no change in the enzyme's function.
e. The enzyme will bind the substrate but not be able to release the products.An epitope is ____
a. the antigen binding site of an antibody molecule b. found only in IgG and IgM c. part of an antigen that binds to a specific antibody d. too small to stimulate an immune response e. a complement protein that initiates lysis of target cells
When does replication of DNA occur?
a. during the S phase b. during the G1 phase c. during the prophase d. during the G0 phase
Review the organisms that cause opportunistic mycoses and their predisposing factors by completing the sentence. Two other opportunistic fungal infections are seen at high rates in __________ patients.
> Pneumocystis jiroveci > AIDS > Aspergillus > Thrush > Candida albicans > Antibiotics > Cryptococcus