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Questions and Answers
What is the primary focus of forensic serology?
Which of the following is NOT a component of blood?
What percentage of blood content is plasma?
Which test is commonly used for identifying blood type?
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What is one of the roles of blood in the human body?
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What percentage of a person's weight does blood account for?
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What is the lifespan of a red blood cell (RBC)?
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Which of the following components primarily functions in blood clotting?
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Which type of cell accounts for the highest proportion of all blood cells?
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What is the primary function of leukocytes?
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How much of blood content does plasma constitute?
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What method is used to presumptively test for the presence of blood?
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Which statement about white blood cells is correct?
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What colour does LeuchoMalachite Green produce in the presence of blood?
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Which of the following is a limitation of Luminol in blood detection?
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What must occur after a presumptive test indicates the presence of blood?
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What is the primary purpose of the Precipitin Test?
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Which animal is typically used in the Precipitin Test procedure?
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Why is ABO blood typing not specific enough for identifying suspects?
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What is the main advantage of DNA testing over ABO typing?
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What occurs if a precipitate forms when mixing the suspected bloodstain extract with antiserum?
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Which blood type contains both A and B antigens?
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Which blood type is most common among indigenous peoples and Latin Americans?
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What test is used to locate and characterize seminal fluid stains?
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What does a purple color indicate in the acid phosphatase test?
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How are the types of blood classified based on the presence of antigens?
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What is the main purpose of forensic serology?
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Which enzyme is specifically associated with saliva?
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What type of protein is detected by the p30 test in seminal fluid?
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Which of the following is NOT a presumptive test for saliva?
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What is the primary function of the antibacterial compounds found in saliva?
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Which body glands are responsible for the production of saliva?
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Which of the following electrolytes is NOT typically found in saliva?
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At what wavelength does the 'woods lamp' emit UV light for detecting fluids?
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Study Notes
Forensic Serology
- A branch of forensic science dedicated to the analysis and identification of biological evidence, including blood, semen, saliva, sweat, breast milk, and other bodily fluids.
- Focuses on detecting enzymes and antigens, such as blood typing.
- Involves characterizing unknown stains, identifying bodily fluids, blood typing, analyzing blood spatter, and paternity testing.
Blood
- A specialized body fluid composed of plasma, red blood cells, white blood cells, and platelets.
- Vital functions include:
- Delivering oxygen and nutrients
- Removing waste products
- Fighting infections
- Regulating body temperature
- Composed of cells, inorganic substances, enzymes, water, and proteins.
- 55% of blood content is plasma, mainly water with dissolved substances.
- Most solid materials are cells:
- Red blood cells (erythrocytes)
- White blood cells (Leukocytes)
- The average human body contains about 5 liters of blood (less for females, more for males).
- Blood constitutes 8% of body weight.
- Oxygenated blood is bright red, while deoxygenated blood is darker red due to hemoglobin.
Red Blood Cells (RBCs)
- Also known as erythrocytes.
- Contain hemoglobin and distribute oxygen throughout the body.
- Account for roughly 93% of all blood cells.
- Approximately 5 trillion cells per liter of blood.
- Represent around 25% of all cells in the body.
- More than 2 million are produced every second.
- Have a lifespan of about 120 days and then get recycled.
- Hematocrit measures RBC volume, representing 45% of whole blood.
White Blood Cells (WBCs)
- Also known as leukocytes.
- Function in the immune system.
- Five types, categorized by immune target and function.
- Account for approximately 0.1% of all blood cells.
- Around 7 billion cells per liter of blood.
- Live for 3-4 days before being recycled.
- Main component of pus.
Thrombocytes
- Responsible for blood clotting.
- Produced by fragmentation of larger stem cells.
- Account for roughly 7% of all blood cells.
- Around 250 billion cells per liter of blood.
- Have a "lifespan" of 5-9 days before being recycled.
- Form long fibers to trap red blood cells and create a scab.
Plasma
- The liquid portion of blood, making up 55% of blood content.
- Primarily water, containing clotting factors, other proteins, hormones, and various chemicals.
- Serum is the liquid that separates from the blood during clot formation (serum = plasma - clotting factors).
Blood at a Crime Scene
- Forensic investigators must answer three crucial questions:
- Is it blood?
- If yes, is it human blood?
- If yes, can it be associated with an individual?
Presumptive Tests for Blood
- Rely on hemoglobin's ability to catalyze the oxidation of certain reagents, often resulting in a color change.
- Hydrogen peroxide (H2O2) is typically used as the oxidizing agent.
- Examples include:
- Kastle-Meyer test (phenolphthalein): Produces a bright pink color in the presence of blood.
- LeuchoMalachite Green test: Similar procedure to the Kastle-Meyer test, producing a blue-green color in the presence of blood.
- Luminol: Used for large areas where blood is suspected but not visible, creating a glow in the presence of blood when viewed in darkness.
Limitations of Presumptive Tests
- Other substances besides blood can cause positive results.
- Luminol can give false positives when exposed to bleach, certain metals, or some vegetables.
- Blood is the only body fluid that will consistently yield a positive result.
- Confirmation with a precipitin test is essential once a positive result is obtained.
Human vs. Non-Human Blood
- The precipitin test confirms whether a bloodstain is human.
- This test identifies proteins unique to human blood.
Precipitin Test Procedure
- An animal (often a rat or rabbit) is injected with human blood.
- The animal's blood forms antibodies.
- Antibodies are extracted from the animal's blood serum (antiserum).
- A suspected bloodstain extract is added to the antiserum in a test tube.
- If a precipitate forms at the point of contact, the blood is human.
Individual Identification with Blood
- Blood typing (ABO system) is a relatively simple method for identifying suspects.
- DNA analysis is a more complex and thorough method for individual identification.
Blood Typing (ABO System)
- Determines antigens present on an individual's red blood cells.
- Blood types:
- Type A: Contains "A" antigen on RBCs.
- Type B: Contains "B" antigen on RBCs.
- Type AB: Contains both "A" and "B" antigens.
- Type O: Contains no A or B antigens.
- Rh factor:
- Rh+: Contains Rh antigen.
- Rh-: Does not contain Rh antigen.
- Not as specific as DNA analysis, but can be useful in narrowing down suspects based on blood type frequency.
Seminal Fluid
- Often examined in sexual offense cases to identify the presence of seminal stains.
- Microscope examination is a confirmatory test, but it can be time-consuming.
- Acid phosphatase, an enzyme secreted into seminal fluid, is used for rapid detection and characterization.
- A purple color indicates the presence of acid phosphatase.
- The p30 test detects human prostate-specific p30 protein found in seminal fluid.
- UV light, a "Woods lamp" at 365nm, can also help identify seminal fluid.
Saliva
- Digestive fluid produced by salivary glands (parotid, sublingual, and submandibular).
- Primarily composed of:
- Water
- Mucus
- Enzymes (alpha-amylase, lingual lipase)
- Electrolytes (Na, K, Ca, Mg, Cl, bicarbonate, phosphate)
- Antibacterial compounds (thiocyanate, H2O2, secretory immunoglobulin A)
Presumptive Tests for Saliva
- Four main tests:
- Amylase: Sensitive to the detection of saliva.
- Phosphatase: Sensitive, but not specific to saliva.
- Nitrite: Sensitive to recent specimens.
- Thiocyanate: Sensitive, but absence does not exclude the presence of saliva.
Summary
- Forensic serology investigates the presence and authenticity of bodily fluids (saliva, semen, or blood) collected at crime scenes.
- Tests are divided into presumptive and confirmatory categories.
- Tests utilize either antibody-antigen interactions or chemical reactions.
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Description
Explore the fascinating intersection of forensic science and biology with this quiz on forensic serology and blood. Delve into the identification of biological evidence, the functions of blood, and various testing methods utilized in criminal investigations. Test your knowledge on blood composition, types, and their importance in forensic analysis.
