Place the steps in the correct order to reflect how a lethal dose may be determined.1. Dilutions of virus are made to represent a range of concentrations.2. Dilutions are inoculated into susceptible tissue cultures (or susceptible host organisms).3. Inoculated host cells are observed and the number of dead cells are counted.4. The dilution which killed 50% of the tissue culture cells is identified.
Fill in the blank(s) with the appropriate word(s).
1, 3, 2, 4
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A patient is diagnosed with gas gangrene in the skin as a result of bullous lesions associated with sepsis. The Gram-stain reaction and morphologic features of the most probable pathogen causing this infection is:
a. gram-positive cocci. b. gram-positive bacilli. c. gram-negative coccobacilli. d. gram-negative bacilli.
The nontranscribed region of DNA to which RNA polymerase binds to initiate transcription is called the ________.
A. intron B. operon C. operator D. exon E. promoter
An organelle found in plant cells and some members of the kingdom Protista but not in animal cells is a
A. chloroplast. B. lysosome. C. Golgi apparatus. D. rough endoplasmic reticulum. E. mitochondrion.
Which of the following is NOT true of
polysaccharides? a. composed of many linked monosaccharides b. may be straight and unbranched or highly branched c. most likely made of glucose molecules if they are one of the natural polysaccharides d. may be insoluble because of their large size and structure e. are formed by cleavage reactions