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Questions and Answers
What is the primary step in determining the species origin of a blood sample?
What is the primary step in determining the species origin of a blood sample?
How is the sex of a person determined from a biological sample?
How is the sex of a person determined from a biological sample?
What type of samples are typically analyzed in a DNA analysis case?
What type of samples are typically analyzed in a DNA analysis case?
What is the purpose of a differential extraction technique in seminal stains?
What is the purpose of a differential extraction technique in seminal stains?
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Who typically conducts the analyses of biological evidence?
Who typically conducts the analyses of biological evidence?
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What is used to identify seminal stains?
What is used to identify seminal stains?
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Which of the following body fluids cannot be typed?
Which of the following body fluids cannot be typed?
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What is the primary purpose of identifying seminal stains in forensic analysis?
What is the primary purpose of identifying seminal stains in forensic analysis?
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Which of the following can be identified by the presence of amylase?
Which of the following can be identified by the presence of amylase?
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Why are private laboratories used in forensic analysis?
Why are private laboratories used in forensic analysis?
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Study Notes
ABO Blood Group System
- ABO blood group system has three alleles: A, B, and O
- A and B alleles are dominant over O
- Individuals with AO genotype have A phenotype
- Individuals with OO genotype have O phenotype
- Individuals with AB genotype have AB phenotype due to codominance of A and B alleles
- Agglutination tests can identify A and B characteristics in AB blood type
Presumptive Blood Tests
- Used to identify blood at crime scenes
- Based on color change or chemiluminescence of reagents when in contact with haemoglobin
- Luminol is commonly used, but can react with other substances like bleach, saliva, and animal/vegetable proteins
Body Fluids
- Liquids originating from inside the human body
- Include fluids secreted or excreted from the body
- Examples: bile, blood serum, breast milk, gastric juice, mucus, saliva, sebum, semen, sweat, tears, vomit, urine
Types of Bodily Fluids
- Secreted: produced by cells, glands, or organs
- Excreted: waste produced by the body, eliminated through processes like fecal matter, urine, tears, carbon dioxide, vomit, and sweat
Bodily Fluids as Evidence
- Found on or about the body of a crime victim
- Common bodily fluids found: blood, semen, and saliva
- DNA analysis can identify individuals based on genetic factors
- DNA typing has high power of discrimination and can be used for identification and characterization
Blood
- Red fluid that circulates in veins and arteries
- Functions: transport system, defense against infection
- No substitute for blood; cannot be made or manufactured
- Rhesus (Rh) blood type: Rh positive (83% in Australia) or Rh negative (17% in Australia)
Blood Group Compatibility
- Plasma contains Anti-A and Anti-B antibodies depending on blood group
- Patients should only receive plasma that does not contain an antibody that could attack their own red cells
Plasma Compatibility
- Group O people have both Anti-A and Anti-B; group O plasma can only be given to group O patients
- Group A plasma contains anti-B; can only be given to patients who are group A or O
- Group B plasma contains anti-A; can only be given to patients who are group B or O
Detecting Semen
- Ultraviolet light causes semen to fluoresce
- Acid phosphatase test is used to detect semen, but can also react positively with other bodily fluids
- Prostate-Specific Antigen (PSA) is used to detect semen, but can also be found in urine
- Microscopic detection of sperm is a more confirmatory method
Blood Evidence Value
- Valuable in crimes like murder, rape, assault, robbery, and burglary
- Can aid investigation by locating crime scene, identifying weapon, proving or disproving alibi, and eliminating suspects
- DNA profiling can be performed on any biological substance
Information Determined
- Analysis must determine if a stain is blood, and then determine species origin
- If human, further classification is achieved by isoenzyme and DNA analysis
- Sex of the person can be determined by DNA typing
- Private laboratories are used for DNA analysis in paternity cases
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Description
Understanding the possible genotypes and phenotypes of ABO blood types based on parental alleles. Learn how to determine offspring genotypes and phenotypes.
