#Question id: 4109
#Unit 1. Molecules and their Interaction Relevant to Biology
When E. coli is grown on a medium containing a mixture of glucose and lactose, it proliferates with complex kinetics. The bacteria proliferate faster at the beginning than at the end, and there is a lag between these two phases when they virtually stop dividing. Assays of the concentrations of the two sugars in the medium show that glucose falls to very low levels after a few cell doublings, but lactose remains high until near the end of the experimental time course (not shown). Although the concentration of lactose is high throughout most of the experiment, β-galactosidase, which is regulated as part of the Lac operon, is not induced until more than 100 minutes have passed. Choose correct explanation why the Lac operon is not induced by lactose during the rapid initial phase of bacterial proliferation
A. The rapid bacterial growth at the beginning of the experiment results from the metabolism of glucose. The slower growth at the end results from metabolism of lactose.
B. CAP and the Lac repressor mediate induction in the situation
C. The bacteria stopped growing in the middle of the experiment because they ran out of glucose but did not yet possess the enzymes necessary for lactose metabolism
D. Induction of the Lac operon requires that two conditions be met: lactose must be present and glucose must be absent.
#Question id: 13187
#Unit 10. Ecological Principles
The following figure is a model of seedling establishment as a function of distance from a parent tree. Initial seed density measures the number of seeds falling to the ground. Seed survivorship measures the proportion of seeds that survive to the adult stage at each distance
Which of the following factors is most likely to generate the seed density curve shown?
#Question id: 2106
#Unit 2. Cellular Organization
When using immunofluorescence microscopy with labeled Annexin V antibodies you found that there is a change in the distribution of the fluorescence when the cells were treated with tumor necrosis factor, an apoptosis-inducing agent. Your data show that this increase in Annexin V fluorescence increases specifically in the:
#Question id: 26855
#Unit 10. Ecological Principles
Linkage density is define by
#Question id: 10495
#Unit 6. System Physiology – Plant
Guard cells have different mechanisms mediating responses to blue light. The npq1 mutant has a lesion in the enzyme that covert violaxanthin to zeaxanthin. What will causes if the npq1 mutant?