E. coli 0157:H7
A. is Gram-positive.
B. is a normal constituent of the intestinal tract.
C. does not ferment sorbitol.
D. produces a toxin.
E. does not ferment sorbitol AND produces a toxin.
E
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Which of the following is the strongest
evidence for the idea that present-day eukaryotic aerobes are the descendants of the successful symbiotic association of anaerobes and aerobes? a. Mitochondria can produce ATP. b. A mitochondrion can survive indefinitely when removed from a eukaryotic cell. c. A mitochondrion has its own set of DNA molecules. d. Fossilized mitochondria are older than the oldest fossilized eukaryotes. e. All eukaryotic cells have mitochondria
The blood-brain barrier consists of
a. membranes surrounding the neurons of the brain. b. cells lining the wall of the brain capillaries. c. vesicles of cerebrospinal fluid. d. the cerebral cortex. e. the meninges.
In looking for a gene responsible for albinism in humans, a group of researchers decided that at least one form of this condition was due to a lack of the enzyme tyrosinase
With this decision as a starting point, which of the following series of steps was most feasible? A) Sequence the amino acids of the protein, use rabbits to make an antibody to the protein, purify and fluorescently label the protein, and hybridize the antibody to a cDNA library. B) Sequence the protein, use the code table to figure out the best RNA sequence for it, synthesize the RNA, and use the RNA as a probe in cells from albino individuals. C) Radioactively tag the enzyme and use it as a probe to identify the biochemical reaction in which it functions, work out the metabolic pathway involved, and find cells in albinos that cannot carry out these reactions. D) Sequence the protein, work out the cDNA that codes for it, label the cDNA code, and use a FISH study to localize the gene on a karyotype. E) Sequence the appropriate region from albino and non-albino cells and compare the sequences or do subtractive hybridization to see where there is a deletion.
In order to fit within a cell, DNA becomes more compact by
A.) breaking apart into separate genes B.) extending to form very long, thin molecules C.) wrapping tightly around histones D.) being enzymatically changed into a protein