Nokea
The anticodons are located in
- A. tRNA.
- B. rRNA.
- C. mRNA.
- D. ribosomes.
Correct Answer: A
Rationale: The correct answer is A: tRNA. Anticodons are sequences of nucleotides found on tRNA molecules that complement the codons on mRNA during translation. tRNA molecules carry specific amino acids to the ribosome based on the codon-anticodon pairing. Option B, rRNA, forms the structure of the ribosome and is not directly involved in anticodon recognition. Option C, mRNA, contains codons but not anticodons. Option D, ribosomes, are the site of protein synthesis but do not contain the anticodons themselves.
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Which of the following bacteria are capable of surviving in both aerobic and anaerobic environments?
- A. Obligate aerobes
- B. Facultative anaerobes
- C. Obligate anaerobes
- D. Microaerophiles
Correct Answer: B
Rationale: The correct answer is B: Facultative anaerobes. Facultative anaerobes can survive in both aerobic and anaerobic environments. In aerobic conditions, they use oxygen for energy production, while in anaerobic conditions, they can switch to fermentation or anaerobic respiration.
A: Obligate aerobes require oxygen to survive and cannot survive in anaerobic environments.
C: Obligate anaerobes cannot survive in the presence of oxygen and only thrive in anaerobic conditions.
D: Microaerophiles require low levels of oxygen to survive and cannot thrive in fully aerobic or anaerobic conditions.
The function of catalase in bacteria is to:
- A. decompose hydrogen peroxide
- B. synthesize peptidoglycan
- C. assist in oxidative phosphorylation
- D. produce endotoxins
Correct Answer: A
Rationale: The correct answer is A: decompose hydrogen peroxide. Catalase is an enzyme that breaks down hydrogen peroxide into water and oxygen. This is important in bacteria to protect them from the harmful effects of hydrogen peroxide, a byproduct of metabolism. Choice B is incorrect as peptidoglycan synthesis is not the function of catalase. Choice C is incorrect as oxidative phosphorylation is a metabolic process unrelated to catalase function. Choice D is incorrect as endotoxin production is not a role of catalase.
Degenerative changes resulting from viral propagation in infected cell cultures are referred as:
- A. Cytolytic effect
- B. cytopathic effect
- C. cytotoxic effect
- D. all three answers are correct
Correct Answer: B
Rationale: The correct answer is B: cytopathic effect. When viruses infect cell cultures, they induce degenerative changes known as cytopathic effects, which include cell shrinkage, rounding, detachment, and cell death. This term specifically refers to the damage caused by viral replication within the cells.
A: Cytolytic effect refers to the destruction of cells by viruses, which is a more specific type of cytopathic effect involving cell lysis.
C: Cytotoxic effect typically refers to the toxic effects of substances on cells, not specifically related to viral propagation.
D: The statement that all three answers are correct is incorrect as only option B accurately describes the degenerative changes resulting from viral propagation in infected cell cultures.
A patient presented with fever, malaise, and an ulcerated lesion. A Gram stain of the lesion revealed large, Gram-positive rods. What is the likely causative agent?
- A. Bacillus anthracis
- B. Clostridium perfringens
- C. Clostridium tetani
- D. Bacillus cereus
Correct Answer: A
Rationale: The correct answer is A: Bacillus anthracis. Bacillus anthracis is the likely causative agent as it is a Gram-positive rod-shaped bacterium known to cause ulcerated lesions with associated fever and malaise. Anthrax typically presents with these symptoms and fits the description given in the question. Clostridium perfringens (Choice B) causes gas gangrene and typically presents with different symptoms. Clostridium tetani (Choice C) causes tetanus and is not associated with ulcerated lesions. Bacillus cereus (Choice D) is known for causing food poisoning and does not typically present with the symptoms described in the question.
A patient has severe catarrhal symptoms. Material growth on Bordet-Gengou agar showed mercury- drop like colonies. Examination of the blood smears revealed some small ovoid gram-negative bacilli sized 1-3 microns. What microorganisms were isolated?
- A. Bordetella
- B. Corynebacteria
- C. Mycobacteria
- D. Meningococcus
Correct Answer: A
Rationale: The correct answer is A: Bordetella. The presence of mercury-drop like colonies on Bordet-Gengou agar indicates Bordetella pertussis. The small ovoid gram-negative bacilli sized 1-3 microns are characteristic of Bordetella species. Catarrhal symptoms are typical of pertussis caused by Bordetella pertussis.
Summary of other choices:
B: Corynebacteria do not typically exhibit mercury-drop like colonies or small ovoid shapes.
C: Mycobacteria are acid-fast bacilli and do not grow on Bordet-Gengou agar.
D: Meningococcus is a gram-negative diplococcus and does not match the description provided.