If a pathogen penetrates nonspecific physical and chemical surface barriers, it breaks through the ________
A) first line of defense
B) second line of defense
C) third line of defense
D) first and second lines of defense
A
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An individual who shelters an infectious agent long after recover is called a(n) _____ carrier.
a. incubation b. chronic c. passive d. asymptomatic e. convalescent
Bacterial and yeast artificial chromosomes are useful tools in molecular biology because
A) they can be used to directly infect human cells and thus treat genetic diseases. B) they are easy to genetically modify and insert into many different organisms. C) they can replace the natural chromosomes found in bacteria and yeast. D) they can carry large DNA fragments (>30,000 bp) such as large eukaryotic genes. E) they are easy to genetically modify and insert into many different organisms, including the direct infection of human cells for the treatment of genetic diseases.
Genetic drift affects a large population more than a small population
a. true b. false