Serology

Plasma

Fluid portion of blood, ~55% of blood and mostly water.

Red Blood Cells (Erythrocytes)

Cells that carry oxygen; contain hemoglobin.

White Blood Cells (Leukocytes)

Cells responsible for immune response.

Platelets

Cell fragments involved in blood clotting.

Antigen

Surface protein on red blood cells that determines blood type and triggers antibody production.

Antibody

Protein made by the immune system that binds a specific antigen; usually bivalent.

Agglutination

Clumping reaction when antibodies bind multiple red blood cells.

Type A Blood

Has A antigens and anti-B antibodies.

Type B Blood

Has B antigens and anti-A antibodies.

Type AB Blood

Has both A and B antigens and no antibodies.

Type O Blood

Has no A or B antigens and has both anti-A and anti-B antibodies.

Rh Factor (D Antigen)

Presence of D antigen makes blood Rh positive.

Immunoassay

Test using antigen-antibody binding to detect specific substances.

Polyclonal Antibodies

Antibodies that bind multiple antigen sites; produced naturally.

Monoclonal Antibodies

Lab-produced antibodies that bind a single antigen site.

EMIT (Enzyme-Multiplied Immunoassay Technique)

Drug test where labeled and unlabeled drugs compete for antibody binding sites.

Presumptive Test

Test that suggests a substance may be present; may react with non-target substances.

Confirmatory Test

Test that specifically identifies one substance.

Kastle-Meyer Test (Phenolphthalein Test)

Presumptive test for blood; heme catalyzes phenolphthalin to pink phenolphthalein.

Positive Phenolphthalein Result

Immediate pink color after phenolphthalin and hydrogen peroxide.

Negative Phenolphthalein Result

No immediate pink color.

Inconclusive Phenolphthalein Result

Pink before peroxide OR sample too pink to interpret.

False Positives for Phenolphthalein

Plant peroxidases, metal oxidizers, bleach, OxiClean, chemical oxidants.

Luminol

Chemical that produces blue luminescence with trace blood; extremely sensitive.

Bluestar

Similar to luminol, glows to reveal bloodstain patterns.

Precipitin Test

Determines species origin of blood using human or animal antisera.

Gel Diffusion

Antigen and antibody diffuse toward each other forming a visible line of precipitation.

Gene

Unit of heredity made of DNA.

Chromosome

DNA structure containing genes; humans have 46 chromosomes.

Allele

Alternative form of a gene at a locus.

Homozygous

Two identical alleles.

Heterozygous

Two different alleles.

Dominant Allele

Expressed trait.

Recessive Allele

Hidden unless homozygous.

Semen

Spermatozoa suspended in seminal fluid.

Spermatozoa

Haploid male gametes; sperm cells.

Acid Phosphatase Test (AP Test)

Presumptive semen test; purple color indicates enzyme activity.

p30 / PSA

Seminal protein detected in immunoassays; not fully confirmatory because found in other fluids.

Christmas Tree Stain

Differential stain where sperm heads stain red/pink and tails green; epithelial cells stain green.

Aspermia

Complete lack of semen.

Azoospermia

Semen without sperm cells.

Persistence: Sperm with Tails

Detectable for 4-6 hours.

Persistence: Sperm without Tails

Detectable for 3-6 days.

Persistence: Acid Phosphatase

Detectable for less than 48 hours.

Persistence: p30 / PSA

Detectable for less than 72 hours.

Alternate Light Source (ALS)

Light source used to locate hidden body fluids by fluorescence.

Flavin

Component of semen that fluoresces under ALS.

Amylase

Enzyme found in high concentration in saliva; target of SALIgAE test.

Buffer

Solution that resists changes in pH.

Catalyst

Chemical that accelerates a reaction.

Contamination

Unwanted DNA introduced to evidence.

Cross-Reaction

Non-target substance causing a positive test.

False Positive

Positive test caused by something other than the target substance.

Sensitivity

Ability of a test to detect small amounts.

Specificity

Ability of a test to detect only the intended substance.

Reference Sample

Known DNA sample, typically a buccal swab or FTA card.

Tamm-Horsfall Protein

Protein in urine; target of RSID-Urine test.

Urobilinogen

Compound in feces; target of fecal material tests.

Phenolphthalin

Reduced, colorless form used in Kastle-Meyer test.

Phenolphthalein

Pink oxidized form produced in positive Kastle-Meyer reactions.

Order of Kastle-Meyer Reagents

Sample, 2. Phenolphthalin, 3. Hydrogen peroxide.

Oxidant Interference

Pink color before peroxide indicates a chemical oxidant.

Overlay Method

Moistened filter paper touches stain to transfer material.

Scraping Method

Filter paper scrapes dried stain for testing.

Direct Test

Testing directly on stain cutting; used for old stains.

Paper Packaging

Used for biological evidence to prevent moisture and bacterial growth.

No Plastic Packaging

Plastic traps moisture and accelerates DNA degradation.

Separate Packaging

Each item packaged individually to avoid contamination.

Refrigeration of Evidence

Prevent DNA degradation before lab analysis.

Sexual Assault Evidence - Victim

Includes vaginal, cervical, rectal, oral swabs; pubic combings; hairs; clothing; blood; buccal swab; urine.

Sexual Assault Evidence - Suspect

Collect clothing, head/pubic hairs, penile swabs, and reference DNA sample.

Transfer

Movement of DNA between surfaces or individuals.

Trace DNA

DNA present even without visible body fluid