The MOST likely cause of Crohn disease is:
A) autoantibody destruction of the intestinal wall.
B) precancerous lesions in the lower intestinal tract.
C) chronically high triglyceride levels in the blood.
D) infection of the gastrointestinal tract with Helicobacter pylori.
Ans: A) autoantibody destruction of the intestinal wall.
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A microbiologist would like to use a noncompetent genus of streptococcal bacteria, Enterococcus faecalis, as a cloning host to express genes from Streptococcus pneumoniae, which is naturally competent. Is this possible?
A. Yes; electroporation or chemical transformation can be used to make non-competent Streptococcus mutants, from which genes can be inserted into a cloning vector and introduced into Enterococcus. B. Yes; since the cloning host and the DNA to be introduced are both from bacteria that are streptococci, natural competence in this case is not necessary as long as the appropriate vector is used. C. Yes; electroporation or chemical transformation can be used to make Enterococcus competent, and then genes from Streptococcus can be introduced via a cloning vector. D. No; competence factor is an essential protein that enables the uptake of foreign DNA, therefore a cloning host such as Enterococcus that lacks competence factor protein is unable to be transformed by electroporation or chemical transformation.
The result obtained in Jacob and Monod's merodiploid analysis that suggested the lacO region acts in cis to regulate the lac operon was:
A. a nonfunctional lacI mutant is rescued by a wild-type lacI allele. B. a nonfunctional lacI mutant cannot be rescued by a wild-type lacI allele. C. a nonfunctional lacO mutant is rescued by a wild-type lacO allele. D. a nonfunctional lacO mutant cannot be rescued by a wild-type lacO allele.
Following are four processes common to most cloning experiments:
transforming bacteria plating bacteria on selective medium cutting DNA with restriction endonucleases ligating DNA fragments Place these components in the order in which they would most likely occur during a cloning experiment.
Give examples of how plants and animal pollinators have coevolved. What will be an ideal response?