TASK DEFINITION: Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.
PROBLEM: Context: Campers Gene and Marie Marsden took pride in being good citizens when in the wild. While driving miles to the Green River Lakes area, they taught their children what they had learned in the bear safety handbook put out by the Bridger-Teton Forest Service. Mr. and Mrs. Marsden did their best to keep a tidy camp. As the handbook had said to hang all food at least ten feet off the ground and four feet out from the trees, they did that and locked their food in their trailer at night. It was already dark when they went to bed, but they _ the campsite with flashlights, making sure nothing was left out. Following the bear book's advice, they slept a hundred yards from where they cooked their food, and kept the car near their tents, separated from the trailer, which they left up at the other camp. The Marsdens liked having their dog Spike on guard. But on the first night, Spike would not stop barking. When Marie Marsden pulled the tent open and shone her flashlight, she saw a young bear. They all piled into the car and drove quickly down the path, calling out of the window to Spike and abandoning the trailer. They drove to a pay phone and called a Fish and Game Department guard, who identified the bear by the white ring of the fur the Marsdens had seen around his neck. The authorities informed the Marsdens that the bear was a young male that they'd been keeping an eye on. The next morning, the Marsdens heard helicopters circling over the mountain and wondered if it might have something to do with the bear. After spending the night in the public campground, they drove back to their site. Wandering the area in search of clues, Marie came to a stop below a tall tree. She slapped her head and shouted, "Oh no!" "What is it?" Gene asked. Marie pointed at the ground where Spike's dog food bowl lay upside down. A week after their return home, the Marsdens read the headline in their local paper. "Bear Killed in Wind Rivers." According to the article, the Fish and Game Department had shot the young bear because, having been rewarded for invading a human campsite, it would likely to do so again. The Marsdens knew they had been lucky in the encounter, yet much to their shame and sadness, they also knew that the bear had not. 
 Question: Who is mostly to blame for the bear's death according to the writer?

SOLUTION: the marsdens.

PROBLEM: Context: Transcription-coupled repair (TCR) is a subpathway of nucleotide excision repair (NER) that acts specifically on lesions in the transcribed strand of expressed genes. First reported in mammalian cells, TCR was then documented in Escherichia coli. In this organism, an RNA polymerase arrested at a lesion is displaced by the transcription repair coupling factor, Mfd. This protein recruits the NER lesion-recognition factor UvrA, and then dissociates from the DNA. UvrA binds UvrB, and the assembled UvrAB* complex initiates repair. In mutants lacking active Mfd, TCR is absent. A gene transcribed by the bacteriophage T7 RNA polymerase in E. coli also requires Mfd for TCR. The CSB protein (missing or defective in cells of patients with Cockayne syndrome, complementation group B) is essential for TCR in humans. CSB and its homologs in higher eukaryotes are likely functional equivalents of Mfd. 
 Question: Which gene strand is targeted by transcription-coupled repair (TCR)?

SOLUTION: the transcribed strand

PROBLEM: Context: The Bacillus anthracis toxin genes, cya, lef, and pag, can be viewed as a regulon, in which transcription of all three genes is activated in trans by the same regulatory gene, atxA, in response to the same signal, CO2. In atxA+ strains, toxin gene expression is increased 5- to 20-fold in cells grown in 5% CO2 relative to cells grown in air. CO2-enhanced toxin gene transcription is not observed in atx4-null mutants. Here, we used two independent techniques to obtain evidence for additional CO2-induced atxA-regulated genes. First, total protein preparations from atxA4+ and atxA isolates grown in 5% CO2 and in air were examined by two-dimensional electrophoresis. Comparison of the resulting protein patterns indicated that synthesis of non-toxin proteins is influenced by growth in elevated CO2 and the toxin gene regulator, atxA. Second, we generated random transcriptional lacZ fusions in B. anthracis with transposon Tn917-LTV3. Transposon-insertion libraries were screened for mutants expressing CO2-enhanced atxA-dependent beta-galactosidase activity. DNA sequence analysis of transposon insertion sites in 17 mutants carrying CO2- and atxA-regulated fusions revealed 10 mutants carrying independent insertions on the 185-kb toxin plasmid pXO1 which did not map to the toxin genes. The tcr-lacZ fusion mutants (tcr for toxin coregulated) were Tox+, indicating that these genes may not be involved in anthrax toxin gene activation. Our data indicate a clear association of atxA with CO2-enhanced gene expression in B. anthracis and provide evidence that atxA regulates genes other than the structural genes for the anthrax toxin proteins. 
 Question: Which metabolite activates AtxA?

SOLUTION:
bicarbonate