Nokea
Anticodon is:
- A. Produced during the process of replication
- B. A nucleotide triplet on the molecule of mRNA
- C. A nucleotide DNA triplet defining the amino acid which has a specific sequence on the polypeptide chain during the translation
- D. A nucleotide triplet forming a unit of genetic code in a transfer RNA molecule corresponding to a complementary codon on messenger RNA
Correct Answer: D
Rationale: The correct answer is D because an anticodon is a nucleotide triplet in a tRNA molecule that pairs with a complementary codon on mRNA during translation. Step 1: Anticodons are found in tRNA, not in DNA or mRNA. Step 2: Anticodons specifically bind to codons on mRNA to ensure correct amino acid incorporation into the growing polypeptide chain, making option D the most accurate choice. Option A is incorrect as replication does not involve anticodons. Option B is incorrect because codons, not anticodons, are found on mRNA molecules. Option C is incorrect as it describes a codon on DNA, not an anticodon on tRNA.
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Which of the following pathogens can cause meningitis?
- A. Staph. aureus
- B. Strep. pyogenes
- C. Strep. pneumoniae
- D. None of the above
Correct Answer: C
Rationale: Rationale for choice C (Strep. pneumoniae):
1. Strep. pneumoniae is a common cause of bacterial meningitis.
2. It is a leading pathogen responsible for meningitis in adults and children.
3. It can invade the bloodstream and reach the meninges, causing inflammation.
4. Treatment guidelines often include antibiotics effective against Strep. pneumoniae.
Summary of why other choices are incorrect:
A. Staph. aureus is not a common cause of meningitis.
B. Strep. pyogenes typically causes streptococcal infections but not meningitis.
D. "None of the above" is incorrect as Strep. pneumoniae can cause meningitis.
The human pinworm Enterobius vermicularis lives in the __________ of humans.
- A. duodenum
- B. ileum
- C. transverse colon
- D. rectum
Correct Answer: D
Rationale: The correct answer is D: rectum. Pinworms typically inhabit the rectum area in humans, where they lay their eggs. This is because the female pinworm migrates to the rectum at night to deposit her eggs near the anus. Other choices are incorrect because pinworms do not reside in the duodenum (A), ileum (B), or transverse colon (C) as their primary location is in the lower gastrointestinal tract near the anus.
The so-called “red tide†is generally caused by which of the following organisms?
- A. Lichens
- B. Bacteria
- C. Pfiesteria
- D. Dinoflagellates
Correct Answer: D
Rationale: The correct answer is D: Dinoflagellates. Red tides are caused by the rapid growth of certain species of dinoflagellates, which are single-celled algae. These algae produce toxins that can harm marine life and humans. Lichens (A) are not associated with red tides. While some bacteria (B) can contribute to harmful algal blooms, they are not the primary cause of red tides. Pfiesteria (C) is a type of harmful algal species, but it is not the main organism responsible for red tides. Therefore, the correct answer is dinoflagellates (D) due to their ability to cause red tides through toxin production.
A child with diarrhea had stool microscopy revealing cysts with four nuclei. What is the most likely causative agent?
- A. Entamoeba histolytica
- B. Giardia lamblia
- C. Balantidium coli
- D. Trichomonas hominis
Correct Answer: A
Rationale: The correct answer is A: Entamoeba histolytica. This pathogen is known to cause amoebic dysentery, characterized by diarrhea with bloody or mucoid stools. The presence of cysts with four nuclei in the stool microscopy is a characteristic feature of Entamoeba histolytica. Other choices are incorrect because Giardia lamblia typically presents with binucleate cysts, Balantidium coli is a ciliated protozoan, and Trichomonas hominis is a non-pathogenic parasite found in the human intestine.
The catarrhal stage of the whooping cough is characterized by:
- A. Decrease in paroxysms of coughing
- B. Subsequent respiratory infection for many months after the onset of pertussis
- C. Uncontrollable coughing followed by a high pitched 'whoop' sound
- D. Mild respiratory symptoms (mild coughing, sneezing or a runny nose)
Correct Answer: D
Rationale: The correct answer is D because the catarrhal stage of whooping cough is characterized by mild respiratory symptoms such as mild coughing, sneezing, or a runny nose. During this stage, the cough may start to worsen but is not yet severe.
A: Incorrect - Decrease in paroxysms of coughing is not seen in the catarrhal stage; it occurs later in the paroxysmal stage.
B: Incorrect - Subsequent respiratory infection for many months after the onset of pertussis is not a characteristic of the catarrhal stage.
C: Incorrect - Uncontrollable coughing followed by a high pitched 'whoop' sound is typical of the paroxysmal stage, not the catarrhal stage.