Textbook Question
Mark the following statements as true or false. If a statement is false, correct is to make a true statement.
d. Vaccinations are given to induce the production of the inflammatory response.
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21. The Immune System
Introduction to Adaptive Immunity
Problem 25
Textbook Question
An investigator at a crime scene discovers some body fluid on the victim's clothing. The investigator carefully takes a sample and sends it to the crime lab for analysis. On the basis of the analysis of antibodies, could the crime lab determine whether the sample is blood plasma or semen? Explain.
Verified step by step guidance1
Understand the composition of blood plasma and semen: Blood plasma is the liquid portion of blood that contains water, electrolytes, proteins (including antibodies), and other dissolved substances. Semen, on the other hand, is a fluid produced by the male reproductive system that contains sperm cells, enzymes, and proteins, but does not typically contain antibodies.
Recognize the role of antibodies: Antibodies are specialized proteins produced by the immune system to identify and neutralize foreign substances. They are commonly found in blood plasma but are not a component of semen.
Consider the analysis process: The crime lab would test the sample for the presence of antibodies using techniques such as enzyme-linked immunosorbent assay (ELISA) or immunoassays. These methods are designed to detect and quantify antibodies in a sample.
Interpret the results: If antibodies are detected in the sample, it is likely to be blood plasma, as antibodies are a characteristic component of blood plasma. If no antibodies are found, the sample could be semen or another fluid that does not contain antibodies.
Conclude based on evidence: The presence or absence of antibodies in the sample provides a clear distinction between blood plasma and semen. The crime lab can use this information to identify the type of body fluid found on the victim's clothing.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Antibodies
Antibodies are specialized proteins produced by the immune system in response to foreign substances, known as antigens. Each type of antibody is specific to a particular antigen, allowing for the identification of various substances in biological samples. In forensic analysis, the presence of specific antibodies can indicate the type of bodily fluid, such as blood or semen, based on the unique antigens found in those fluids.
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Antibodies
Blood Plasma
Blood plasma is the liquid component of blood, comprising about 55% of its total volume. It contains water, electrolytes, proteins, hormones, and waste products. The proteins in plasma, such as albumin and globulins, can be identified through serological tests, which can help distinguish blood plasma from other bodily fluids, including semen.
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Semen Analysis
Semen analysis involves the examination of seminal fluid, which contains sperm cells and various proteins unique to male reproductive fluid. Specific tests can detect the presence of prostate-specific antigen (PSA) and other markers that are characteristic of semen. By analyzing these components, forensic scientists can differentiate semen from other bodily fluids, such as blood plasma, during criminal investigations.
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