Which statement shows an example of a commensal species in one host becoming a pathogenic species in another host?
A) New infectious diseases are due to increases in host tropism.
B) C. difficile flourishes in the large intestine after antibiotic therapy.
C) E. coli lives harmlessly in the appendix but will be attacked by the immune system if it invades the abdominal cavity.
D) Shigella flexneri preferably infects the tissues of humans and other primates.
E) Up to 30% of pregnant women harbor Group B streptococci in the vagina to no ill effect, but when transmitted to their newborns, a proportion of babies develop serious infection.
Answer: E
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In human gene therapy, genes are transferred by
a. viral vectors or lipid clusters b. bacterial cells. c. bacterial plasmids. d. hypodermic injection. e. tissue transplantation.
What cell structure defines the outer boundary of all cells, separating the cell's contents from its environment? (two words)
What will be an ideal response?
Suppose two genes a and b are 7.4 map units from each other, and that genes b and c are 5.7 map units from each other. You do a cross to determine the map distance between a and c. Which result would indicate that c lies between a and b?
a. 2.0 map units b. 11.1 map units c. 14.8 map units d. 15.0 map units
Which one of the following diseases of the gastrointestinal system is transmitted by the respiratory route?
A) staphylococcal enterotoxicosis B) mumps C) Vibrio gastroenteritis D) bacillary dysentery E) traveler's diarrhea