Nokea
The eukaryotes known for the presence of a macronucleus and a micronucleus are:
- A. algae
- B. fungi
- C. protozoans
- D. slime molds
Correct Answer: C
Rationale: The correct answer is C: protozoans. Protozoans are eukaryotic organisms that possess both a macronucleus, responsible for general cell functions, and a micronucleus, involved in genetic processes like reproduction. Algae (choice A) typically have a single nucleus, fungi (choice B) lack distinct macronucleus and micronucleus structures, and slime molds (choice D) do not have the same nucleus organization as protozoans. Thus, protozoans are the only group among the choices that exhibit the specific characteristics of having both a macronucleus and a micronucleus.
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For the structure of rubella virus is true that
- A. has icosahedral type of symmetry
- B. is ssDAN virus
- C. does not have an envelope
- D. does not have glycoprotein spikes
Correct Answer: A
Rationale: The correct answer is A. Rubella virus has icosahedral type of symmetry due to its spherical shape with 20 faces. This symmetry allows for efficient packaging of genetic material and structural stability. Choice B is incorrect as rubella virus is an ssRNA virus, not ssDNA. Choice C is incorrect as rubella virus does have an envelope derived from the host cell membrane. Choice D is incorrect as rubella virus does have glycoprotein spikes on its surface that aid in host cell recognition and entry.
A phage in a repressed stage is referred to as a(n)
- A. antiphage.
- B. prophage.
- C. virulent phage.
- D. latent phage.
Correct Answer: B
Rationale: The correct answer is B: prophage. In the repressed stage, a phage integrates its DNA into the host cell's chromosome, becoming a prophage. This integration allows the phage to replicate along with the host cell without causing immediate lysis.
A: Antiphage is not a term used to describe a phage in a repressed stage.
C: Virulent phage refers to a phage that immediately causes lysis of the host cell.
D: Latent phage is not a commonly used term in this context.
Which of the following statements concerning Neisseria Meningitidis is correct?
- A. Has no capsules
- B. It causes epidemic meningitis
- C. Grow on differential media
- D. Gram-positive rods
Correct Answer: B
Rationale: The correct answer is B: It causes epidemic meningitis. Neisseria Meningitidis is a bacterium that can cause meningitis, an infection of the protective membranes covering the brain and spinal cord. This bacterium is known to cause outbreaks or epidemics of meningitis, especially in crowded or close-contact settings. The other choices are incorrect because:
A: Neisseria Meningitidis does have a capsule, which helps it evade the immune system.
C: Neisseria Meningitidis grows on selective media like Thayer-Martin agar, not differential media.
D: Neisseria Meningitidis is a Gram-negative diplococcus, not a Gram-positive rod.
Which bacteria produce a toxin that inhibits protein synthesis?
- A. Shigella dysenteriae
- B. Clostridium botulinum
- C. Streptococcus pneumoniae
- D. Mycobacterium tuberculosis
Correct Answer: A
Rationale: The correct answer is A: Shigella dysenteriae. This bacteria produces the Shiga toxin, which inhibits protein synthesis by interfering with the ribosomes. Shigella dysenteriae causes severe gastrointestinal illness. The other choices, B: Clostridium botulinum, produces a neurotoxin that blocks neurotransmitter release. C: Streptococcus pneumoniae causes pneumonia and other respiratory infections. D: Mycobacterium tuberculosis causes tuberculosis by infecting the lungs. Thus, based on the toxin production and mode of action, Shigella dysenteriae is the correct answer.
In which of the following especially dangerous infections, the respiratory tract is not damaged:
- A. Tularemia
- B. Plague
- C. Anthrax
- D. Cholera
Correct Answer: D
Rationale: The correct answer is D, Cholera. Cholera is caused by the bacterium Vibrio cholerae and primarily affects the intestines, leading to severe watery diarrhea and dehydration. It does not damage the respiratory tract.
Choice A, Tularemia, affects the respiratory tract and other organs. Choice B, Plague, can cause respiratory symptoms like cough and difficulty breathing. Choice C, Anthrax, can affect the respiratory tract if inhaled in its spore form.