A catalase-negative, non–spore forming, nonbranching, gram-positive rod that produces hydrogen sulfide when inoculated into triple sugar iron (TSI) agar is most likely:
a. Corynebacterium.
b. Bacillus.
c. Actinomyces.
d. Erysipelothrix.
D
Erysipelothrix is the only catalase-negative, gram-positive, and non–spore forming rod that pro-duces hydrogen sulfide (H2S) when inoculated into TSI agar. Some Bacillus spp. also blackens the butt of TSI, but it is catalase-positive and produces spores.
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Which of the following statements about genomic libraries and cDNA libraries is TRUE?
A. A cDNA library is derived from chromosomal DNA. B. A genomic library is derived from mRNA. C. A genomic library is made using reverse transcriptase. D. A genomic library is derived from mRNA and is made using reverse transcriptase. E. A cDNA library is derived from mRNA and is made using reverse transcriptase.
In the 1980s and 1990s, positional cloning led to the discovery of genes that
A) encode all proteins in the human genome. B) cause hemophilia, fragile X syndrome, and colorblindness. C) cause several types of cancers. D) cause Duchene muscular dystrophy, cystic fibrosis, and Huntington disease.
Small doses of ionizing radiation over a long period of time cause less damage because
a. they are too low to affect cells. b. they don't hit as many targets. c. the body has time to repair damaged DNA. d. the radiation is absorbed by macrophages. e. the radiation is absorbed by red blood cells.
A student set up an experiment to test if plants give off water vapor. Fifty pea plants, growing in pots, were covered with individual glass containers and left overnight. The next morning, the inside of each lid was covered in droplets of water. The lab student concluded that plants generally give off water vapor. What critique would you make of the experimental design?
A. The student did not have a clearly stated hypothesis before beginning the experiment. B. There was no control so the water could have come from other sources such as air in the jar or the soil. C. The experiment was not precise, meaning it was not reproducible. D. There was not a large enough sample of pea plants used to get adequate data.