Questions Set - 2 Forensic Serology
Q1. In the context of forensic bloodstain pattern analysis, which of the following formulas is used to determine the angle of impact of a blood drop?
A) sin(θ) = width / length
B) tan(θ) = length / width
C) tan(θ) = width / length
D) cos(θ) = width / length
Answer: B) tan(θ) = length / width
Explanation: The angle of impact (θ) of a bloodstain is calculated using the formula tan(θ) = length / width. This helps forensic experts to estimate the angle at which a blood drop strikes a surface, providing insight into the blood source's location.
Q2. In the context of serological discrimination between peripheral and menstrual blood, which of the following best justifies the use of D-dimer immunoassay in forensic casework?
A) D-dimers are degradation products of hemoglobin metabolism
B) D-dimer levels are constant in all blood types
C) Menstrual blood undergoes fibrinolysis leading to elevated D-dimer levels
D) D-dimer is unique to menstrual blood due to estrogen influence
Answer: C) Menstrual blood undergoes fibrinolysis leading to elevated D-dimer levels
Explanation: Menstrual blood, unlike peripheral blood, is subject to endometrial fibrinolysis, which releases D-dimers — a critical distinction in forensic serology.
Q3. Which of the following tests involves the use of monoclonal antibodies to detect human blood, making it more species-specific than traditional tests?
A) Luminol test
B) ABAcard® HemaTrace
C) Takayama crystal test
D) Kastle-Meyer test
Answer: B) ABAcard® HemaTrace
Explanation: The ABAcard® HemaTrace uses monoclonal antibodies to specifically detect human hemoglobin, making it more accurate and species-specific compared to other traditional blood detection tests.
Q4. Which of the following statements regarding the ABAcard® HemaTrace test is false?
A) It can yield false positives with primate blood
B) It uses monoclonal antibodies against human hemoglobin
C) It is a lateral flow immunochromatographic assay
D) It detects Glycophorin A in erythrocyte membranes
Answer: B) It uses monoclonal antibodies against human hemoglobin
Explanation: HemaTrace targets Glycophorin A, not hemoglobin. Hemoglobin-based tests are prone to species cross-reactivity, but Glycophorin A is more human-specific.
Q5. What is the primary legal challenge to the use of acid phosphatase testing as a presumptive test for semen in court?
A) Cross-reactivity with non-biological stains
B) The test is not reproducible
C) Acid phosphatase is not semen-specific and found in high levels in other tissues
D) The test results cannot be digitally documented
Answer: C) Acid phosphatase is not semen-specific and found in high levels in other tissues
Explanation: AP is present in various body fluids and tissues (e.g., vaginal secretions, liver), making its evidentiary value limited without confirmatory tests like PSA or DNA profiling.
Q6. In forensic serology, which of the following is the most common challenge when using the Luminol test for blood detection at crime scenes?
A) Detection of latent blood stains
B) False positives due to the presence of cleaning agents
C) Destruction of DNA samples
D) Inability to differentiate between animal and human blood
Answer: B) False positives due to the presence of cleaning agents
Explanation: The Luminol test reacts with any oxidizing agent, such as bleach or cleaning agents, causing false positives. This makes it difficult to definitively confirm the presence of blood without further testing.
Q7. In forensic serology, what is the most appropriate approach to distinguish between epithelial cells from different contributors in a mixed DNA profile?
A) Differential lysis followed by STR profiling
B) Species-specific immunodiffusion
C) Fluorescence microscopy of ABO antigens
D) mRNA expression profiling of tissue-specific markers
Answer: D) mRNA expression profiling of tissue-specific markers
Explanation: mRNA markers (e.g., MUC4 for vaginal cells, PRM2 for sperm) can differentiate tissue types at the transcriptional level, assisting in contributor differentiation.
Q8. The weak antigenic expression of ABO blood group antigens on epithelial cells is attributed to:
A) Postmortem degradation of surface proteins
B) Lack of Golgi processing
C) Secretor status and tissue specificity
D) Incomplete transcription of ABO alleles
Answer: C) Secretor status and tissue specificity
Explanation: ABO antigens in secretions are controlled by the FUT2 gene. Non-secretors lack ABO antigen expression in fluids and some epithelial cells, complicating blood typing from stains.
Q9. Which molecular test has been demonstrated to retain accuracy even in environmentally degraded semen samples?
A) Acid phosphatase spot test
B) Immunochromatographic PSA detection
C) RNA-based identification using RT-PCR
D) Takayama microcrystal assay
Answer: C) RNA-based identification using RT-PCR
Explanation: mRNA, while labile, can sometimes outlast DNA in degraded samples and offers tissue-specific expression, making it valuable in compromised semen samples.
Q10. Which of the following best describes the forensic value of identifying amylase isoenzymes in a questioned stain?
A) Differentiation of blood from fecal stains
B) Confirmation of semen over sweat
C) Differentiation between salivary and pancreatic origin
D) Indication of ABO group in fluids
Answer: C) Differentiation between salivary and pancreatic origin
Explanation: α-amylase exists in isoforms — AMY1 (salivary) and AMY2 (pancreatic). Identifying AMY1 supports the presence of saliva, which is critical in bite marks or cigarette butts.
Content Writer:- Srishti Dutta
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