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What outcome would you least expect if the amount of template in a PCR fell significantly below the optimal amount?
- A. non-specific amplification
- B. increased yield
- C. Allelic drop-out (some alleles fail to amplify)
- D. Longer targets amplify poorly or fail
Correct Answer: B
Rationale: The correct answer is B: increased yield. If the amount of template in a PCR falls significantly below the optimal amount, it would be expected to result in a decreased yield rather than an increased yield. The template is essential for DNA amplification in PCR, and a lower amount would lead to fewer copies being produced. Non-specific amplification (choice A) can occur if there is too much template or incorrect primer annealing. Allelic drop-out (choice C) is likely to happen if there is insufficient template present to amplify all alleles. Longer targets amplifying poorly or failing (choice D) is also a common outcome when template concentration is low. Therefore, the least expected outcome would be an increased yield as that goes against the principle of PCR amplification.
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What describes a primary use of biologic therapy in cancer treatment?
- A. Protect normal,rapidly reproducing cells of the gastrointestinal system from damage during chemotherapy
- B. Prevent the fatigue associated with chemotherapy and high-dose radiation as seen with bone marrow depression
- C. Enhance or supplement the effects of the host’s immune responses to tumor cells that produce flu-like symptoms
- D. Depress the immune system and circulating lymphocytes as well as increase a sense of well-being by replacing central nervous system deficits
Correct Answer: C
Rationale: Biologic therapy enhances the immune response against tumor cells, often causing flu-like symptoms.
Select the correct statement during an allergic reaction.
- A. An allergen binds with IgE antibodies.
- B. The mast cells are deactivated.
- C. The body is immunodeficient.
- D. Helper T cells release histamine.
Correct Answer: A
Rationale: Step-by-step rationale:
1. During an allergic reaction, allergens trigger the release of IgE antibodies.
2. The allergen binds with IgE antibodies, leading to the activation of mast cells.
3. Activated mast cells release histamine and other inflammatory mediators.
4. This cascade of events causes allergic symptoms.
Therefore, option A is correct as it accurately describes the initial binding of allergen with IgE antibodies. Option B is incorrect as mast cells are activated, not deactivated. Option C is incorrect as the body is hypersensitive, not immunodeficient. Option D is incorrect as it is mast cells, not Helper T cells, that release histamine.
Why is Edward Jenner's experiment on a young boy considered a scientific landmark?
- A. Jenner inoculated the young boy using material obtained from the scabs of a milkmaid who had suffered of a very mild form of smallpox. The boy never contracted the disease.
- B. Jenner inoculated the young boy first using material obtained from the scabs of a milkmaid who had suffered of a very mild form of smallpox; subsequently he inoculated the boy with virulent smallpox.
- C. Variolation was the crude practice of injecting smallpox in a way that would supposedly protect the recipient from getting a fatal form of the disease; Jenner instead injected the young boy with cowpox. The fact that the boy did not die proved that cowpox inoculation protects against smallpox
- D. Jenner noticed the milkmaids were protected from smallpox but were often affected by a mild disease caused by cowpox. He decided to inoculate a young boy with cowpox first and subsequently with smallpox to prove that exposing people to cowpox can make them immune from getting smallpox
Correct Answer: D
Rationale: Step 1: Jenner observed milkmaids were protected from smallpox due to prior exposure to cowpox.
Step 2: Jenner decided to inoculate a young boy with cowpox first.
Step 3: Jenner then inoculated the boy with smallpox to test immunity.
Step 4: The boy did not contract smallpox, demonstrating immunity.
Step 5: Conclusion: Jenner proved cowpox exposure can make individuals immune to smallpox.
Other choices are incorrect:
A: The boy never contracted smallpox, not just because of the mild form of smallpox in the milkmaid.
B: Inoculating with virulent smallpox first would not demonstrate cowpox immunity.
C: Jenner did not just substitute cowpox for smallpox; he specifically tested immunity by exposing the boy to both viruses.
Identify the mismatched receptor: ligand pair
- A. NOD2: peptidoglycan
- B. TLR9: CpG DNA
- C. TLR5: dsRNA
- D. RIG-I: viral RNA
Correct Answer: C
Rationale: TLR5 recognizes flagellin, not dsRNA. This is why choice C is the correct answer. NOD2 binds to peptidoglycan (A), TLR9 binds to CpG DNA (B), and RIG-I recognizes viral RNA (D). Each receptor has specificity for a different ligand, making choice C the mismatched pair.
A patient with systemic lupus erythematosus (SLE) is admitted to the hospital for evaluation and management of acute joint inflammation. Which information obtained in the admission laboratory testing concerns you most?
- A. The blood urea nitrogen (BUN) level is elevated.
- B. The C-reactive protein (CRP) level is increased.
- C. The anti-nuclear antibody (ANA) test is positive.
- D. The lupus erythematosus (LE) cell prep is positive.
Correct Answer: A
Rationale: An elevated BUN level may indicate kidney involvement which is a serious complication of SLE. The other findings are expected in SLE and do not indicate an urgent problem. CRP is a marker of inflammation and positive ANA and LE cell prep are diagnostic of SLE but do not indicate acute complications.