Serology, Blood, DNA Quiz - Forensics

**Serology

** The study of blood serum and other bodily fluids (saliva, semen, urine, sweat).

**Secretor

** An individual (80% of the population) whose blood type antigens are also found in their other bodily fluids.

**Presumptive Test

** A highly sensitive initial screening tool used to narrow down possibilities; it carries a risk of false positives.

**Confirmatory Test

** A conclusive test used to identify a substance with high certainty and low risk of false positives.

**Amylase

** An enzyme found in high concentrations in saliva used for forensic identification.

**Phadebas Test

** A presumptive test for saliva that detects the enzyme amylase.

**RSID (Rapid Stain Identification)

** A confirmatory test used to identify human saliva.

**Acid Phosphatase (AP)

** An enzyme present in high levels in semen; used in presumptive testing.

**Prostate-Specific Antigen (PSA)

** A protein found in semen used as a presumptive marker.

**Christmas Tree Stain

** A confirmatory test for semen that uses red and green dyes to visualize sperm cells under a microscope.

**Karl Landsteiner

** The scientist who discovered the A-B-O blood typing system in 1901.

**Antigens

** Proteins or materials on the surface of red blood cells that can provoke an immune response.

**Antibodies

** Proteins in the blood plasma that bind to specific foreign antigens to neutralize them.

**Type A Blood

** Has A antigens on the red blood cells and anti-B antibodies in the plasma.

**Type B Blood

** Has B antigens on the red blood cells and anti-A antibodies in the plasma.

**Type AB Blood

** Has both A and B antigens; no antibodies in the plasma (Universal Recipient).

**Type O Blood

** Has no antigens; both anti-A and anti-B antibodies in the plasma (Universal Donor).

**Rh Factor

** An additional antigen (D) on red blood cells; its presence makes blood "positive" and its absence "negative."

**Kastle-Meyer Test

** A presumptive blood test using phenolphthalein that turns deep pink in the presence of hemoglobin.

**Luminol

** A chemical that glows (chemiluminescence) to detect trace amounts of blood, even after cleaning.

**Hemastix

** A presumptive test strip that turns green in the presence of blood.

**Precipitin Test

** A confirmatory test using anti-human serum to determine if a bloodstain is of human or animal origin.

**Chromosome

** A structure of DNA and protein; humans have 46 total (23 pairs).

**Allele

** An alternative form of a gene (e.g., the A, B, or O version of the blood type gene).

**Coding Regions (Exons)

** The 3% of human DNA that contains instructions for making proteins.

**Non-coding Regions (Introns)

** The 97% of DNA that does not code for proteins; these highly variable areas are used for forensic "fingerprinting."

**Chargaff’s Rule

** The DNA principle stating that Adenine (A) always pairs with Thymine (T), and Guanine (G) always pairs with Cytosine (C).

**PCR (Polymerase Chain Reaction)

** A technique used to amplify (copy) small amounts of DNA into a larger sample for analysis.

**DNA Primers

** Short DNA sequences used in PCR to identify and "start" the copying process at specific locations.

**STR (Short Tandem Repeats)

** Repeating sequences of 2-10 base pairs in non-coding DNA; the number of repeats is unique to individuals.

**Gel Electrophoresis

** A technique that uses an electric current to separate DNA fragments by size (smaller fragments move faster/further).

**Amelogenin Gene

** A genetic marker used to determine sex; XX (female) shows one band, while XY (male) shows two bands.

**Age and Gender ID

** DNA can determine biological sex; age can be estimated through hormonal concentrations in blood.

**CODIS

** The FBI’s Combined DNA Index System; a national database of DNA profiles from convicted felons and crime scenes.

**Cold Hit

** When a DNA profile from a crime scene matches an unknown suspect already in the CODIS database.

**Passive Spatter

** Bloodstains created by the force of gravity alone (e.g., drops, pools, or clots).

**Transfer Spatter

** Created when a wet, bloody surface comes in contact with another surface (e.g., a bloody handprint).

**Projected Spatter

** Occurs when an internal or external force is applied to a blood source (e.g., impact spatter).

**Point of Convergence

** The common 2D area where the directionality of individual blood drops can be retraced.

**Impact Angle Formula

** The calculation used to find the angle of impact; Inverse Sine of (Width / Length).

**Short Angle / Long Angle Rule

** When calculating impact angle, the smaller number (width) is always divided by the larger number (length).

**Impact Speed (Low/Med/High)

** Categorization of spatter based on the force of the energy hitting the blood source.