Blood and Semen Identification, and DNA
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What are two other terms for a presumptive test?
• PRELIMINARY • SCREENING
What does it mean for a scientific test to be “presumptive”?
IT CAN ONLY “INDICATE” THAT THE BODY FLUID MAY BE PRESENT; IT DOESN’T PROVE CONCLUSIVELY THAT IT IS PRESENT.
What are the two fractions of blood?
• FORMED ELEMENTS • PLASMA
What does it mean for a scientific test to be “confirmatory”?
THIS TYPE OF TEST PROVES THAT THE BODY FLUID IS PRESENT SUCH AS “HUMAN BLOOD IDENTIFIED”
Define the function of the following blood components and state their function: Red blood cells:
GAS EXCHANGE; PICK UP OXYGEN AT THE LUNGS AND CARRY IT TO TISSUES; PICK UP CARBON DIOXIDE IN TISSUES AND CARRY IT TO THE LUNGS
Define the function of the following blood components and state their function: White blood cells:
FIGHT INFECTION
Define the function of the following blood components and state their function: Platelets:
ESSENTIAL IN BLOOD CLOTTING
Define the function of the following blood components and state their function: Plasma:
KNOWN AS THE LIQUID PORTION OF BLOOD. CARRIES EVERYTHING ELSE THAT IS NOT A FORMED ELEMENT SUCH AS VITAMINS, ELECTROLYTES, HORMONES, ANTIBODIES, ENZYMES, ETC.
What is the main presumptive test for blood and what color does it turn if positive?
KM; TURNS PINK
The main protein in blood is ____ which is comprised by 4 iron containing _____ groups.
-HEMOGLOBIN -HEME
The two reagents needed to perform the KM test are:
• HYDROGEN PEROXIDE • KM REAGENT
List four advantages of the KM test:
• SENSITIVE; NEEDS VERY SMALL SAMPLE TO PERFORM • SAMPLE CAN STILL BE USED FOR DNA • COST EFFECTIVE • REAGENTS ARE STABLE AND NON-TOXIC
List three disadvantages of the KM test:
• CROSS REACTS WITH RUST, HORSERADISH, ROOT VEGETABLES • CAN ONLY SAY THAT BLOOD IS “INDICATED” • DOES NOT IDENTIFY SPECIES
Define the following: Luminol:
HIGHLY SENSITIVE PRESUMPTIVE TEST FOR BLOOD; FLUORESCES WHEN SEEN UNDER UV LIGHT
Define the following: Hemastix:
PRESUMPTIVE TEST FOR BLOOD; STICK TURNS GREEN IF POSITIVE
How does the Ochterlony Double Diffusion Test work?
THE ODD TEST IS A PRECIPITIN TEST WHERE AN ANTIGEN (PROTEIN) WILL REACT WITH AN ANTIBODY TO PRODUCE A SOLID PRECIPITATE. WELLS ARE CUT INTO A GEL AND CRIME SCENE SAMPLES (ANTIGENS) CAN BE TESTED AGAINST VARIOUS ANTIBODIES.
Why is the ODD test especially useful in veterinary forensic cases?
THE ODD TEST CAN BE USED TO DETERMINE THE SPECIES (SUCH AS HUMAN, DOG, CAT, ETC) OF THE SAMPLE
Is the ODD test presumptive or confirmatory?
CONFIRMATORY
What is the “ALS” and how it is useful in identifying possible semen stains on items of physical evidence?
ALS stands for “Alternate Light Source”. It is useful because semen will fluoresce under the ALS.
Where is the MAJORITY of the DNA located in a sperm cell?
The head of the sperm cell (which contains all the nuclear DNA from the father)
What other body fluid will fluoresce under the ALS?
Urine
What is the acrosome on a sperm cell and what function does it serve?
The acrosome is located on the tip of the head of the sperm cell. It contains a cluster of enzymes which helps the sperm digest the through the thick layers of the egg so the sperm can enter the egg and fertilization can occur.
True or False: Mitochondrial DNA from the sperm cell does NOT enter the egg when fertilization occurs:
TRUE
True or False: You can have semen WITHOUT sperm, but you CANNOT have sperm without semen.
TRUE