Nokea
While examining the feces of a patient with diarrhea, cysts with four nuclei were found. What protozoan is most likely causing the condition?
- A. Entamoeba histolytica
- B. Lamblia
- C. Trichomonas
- D. Balantidium
Correct Answer: A
Rationale: The correct answer is A: Entamoeba histolytica. This protozoan causes amoebiasis, which presents with symptoms like diarrhea. The cysts with four nuclei found in the feces are characteristic of Entamoeba histolytica. This protozoan is known to cause invasive infection, leading to tissue destruction and ulcers in the intestines. Lamblia (choice B) typically presents with cysts containing two nuclei. Trichomonas (choice C) is a sexually transmitted parasite and does not form cysts. Balantidium (choice D) is a ciliated protozoan that does not have four nuclei in its cyst form.
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Which of the following is a general-purpose medium?
- A. Tryptic soy agar
- B. Blood agar
- C. Mannitol salt agar
- D. MacConkey agar
Correct Answer: A
Rationale: The correct answer is A: Tryptic soy agar is a general-purpose medium suitable for cultivating a wide range of microorganisms. It provides essential nutrients for growth without inhibiting specific types of bacteria. Blood agar (B), Mannitol salt agar (C), and MacConkey agar (D) are selective or differential media designed to promote the growth of specific types of bacteria or differentiate between different bacterial species. Therefore, they are not considered general-purpose mediums.
Production of RNA from DNA is called
- A. Transposition
- B. Translation
- C. Transcription
- D. RNA splicing
Correct Answer: C
Rationale: The correct answer is C: Transcription. Transcription is the process of synthesizing RNA from a DNA template. During transcription, RNA polymerase binds to the DNA and produces a complementary RNA strand. This process is essential for gene expression.
Explanation for why other choices are incorrect:
A: Transposition involves the movement of genetic elements within a genome, not the production of RNA from DNA.
B: Translation is the process of synthesizing proteins from mRNA, not the production of RNA from DNA.
D: RNA splicing is the process of removing introns and joining exons in pre-mRNA to produce mature mRNA, not the initial production of RNA from DNA.
Rod-shaped bacteria, some of which are endospore forming, are referred to as:
- A. cocci
- B. bacilli
- C. spirals
- D. vibrios
Correct Answer: B
Rationale: The correct answer is B. Bacilli are rod-shaped bacteria, some of which are endospore forming. Cocci are spherical, spirals are spiral-shaped, and vibrios are curved rod-shaped bacteria. Bacilli specifically refer to rod-shaped bacteria, making it the correct answer in this context.
Precipitation reaction can be converted into agglutination reaction by coating soluble antigen onto
- A. Bentonite (clay) particles
- B. RBCs
- C. Latex particles
- D. All of these
Correct Answer: D
Rationale: The correct answer is D: All of these. Coating soluble antigen onto Bentonite particles, RBCs, or Latex particles can convert a precipitation reaction into an agglutination reaction. This is because soluble antigens bind to their specific antibodies, causing the particles to clump together, visible as agglutination. Bentonite particles, RBCs, and Latex particles all provide surfaces for the antigen-antibody interaction to occur, leading to agglutination. Therefore, all of these options are correct for converting precipitation reactions to agglutination reactions.
Which bacterial structure allows for attachment to host cells?
- A. Flagella
- B. Fimbriae
- C. Capsule
- D. Endospore
Correct Answer: B
Rationale: The correct answer is B: Fimbriae. Fimbriae are hair-like appendages found on the surface of bacteria that enable attachment to host cells. This attachment is crucial for establishing infection. Flagella (A) are used for movement, not attachment. Capsules (C) provide protection and help evade the host immune system, but do not directly facilitate attachment. Endospores (D) are dormant structures for survival, not for attachment to host cells. Fimbriae specifically aid in adherence to host cells, making them the correct choice in this context.