In Griffith's experiments with Streptococcus pneumoniae, rough non-encapsulated streptococci were converted into smooth encapsulated streptococci in the presence of the heat-killed smooth encapsulated streptococci. Which microbial process had Griffith identified?
transduction
conjugation
transformation
cloning
The Correct Answer is C
A. Transduction: Transduction is gene transfer mediated by bacteriophages (viruses that infect bacteria); Griffith’s experiment did not involve phage activity.
B. Conjugation: Conjugation requires direct cell-to-cell contact and transfer of DNA (often plasmids) via a pilus; Griffith’s work did not depend on cell contact.
C. Transformation: Transformation is the uptake and incorporation of free DNA from the environment by a bacterium; Griffith observed non-encapsulated cells acquiring traits from heat-killed encapsulated cells, which is transformation.
D. Cloning: Cloning refers to producing genetically identical copies or isolating a gene in laboratory techniques; this term does not describe Griffith’s natural gene uptake observation.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
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Correct Answer is A
Explanation
A. True: Ionizing radiation (gamma rays, X-rays) penetrates deeply and causes ionizations that break DNA and other critical molecules, making it generally more effective at inactivating microbes and spores than nonionizing UV, which has more limited penetration.
Correct Answer is A
Explanation
A. Eurytolerant: Refers to organisms that can survive and grow under a wide range of environmental conditions (e.g., temperature, pH, salinity).
B. Stenotolerant: Opposite of eurytolerant; can survive only within a narrow range of conditions.
C. Obligate: Indicates a strict requirement for a particular condition (e.g., obligate aerobe requires oxygen).
D. Facultative: Indicates flexibility with respect to certain conditions (e.g., facultative anaerobes can
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