Alleles. Alternate gene forms or variations, which are the basis of DNA
Antigens. Any biological substance that can stimulate the production of,
and combine with, antibodies. Variances in human antigens can be used to
identify individuals within a population.
DNA. Deoxyribonucleic acid, which contains genetic material and whose shape
resembles a rope ladder that has been twisted (the double helix). An individual's
DNA is unique except in cases of identical twins.
DNA profiling. The process of testing to identify DNA patterns or types.
In the forensic setting, this testing is used to indicate parentage or to
exclude or include individuals as possible sources of body fluid stains (blood,
saliva, semen) and other biological evidence (bones, teeth, hair).
DNA typing. See DNA profiling.
DQ alpha. An area (locus) of DNA that is used by the forensic community
to characterize DNA. Because there exist seven variations (alleles) of DNA
at this locus, individuals can be categorized into one of 28 different DQ
alpha types. Determination of an individual's DQ alpha type involves a Polymerase
Chain Reaction-based test.
Electrophoresis. A technique by which DNA fragments are placed in a gel
and separated by size in response to an electrical field.
Epithelial cells. Membranous tissue forming the covering of most internal
surfaces and organs and the outer surface of the body.
Epithelial cell fraction. One of two products from a differential extraction
that removes DNA from epithelial cells before analysis of sperm DNA can
be conducted. The other product is the sperm cell reaction.
Exclusion. A DNA test result indicating that an individual is excluded as
the source of the DNA evidence. In the context of a criminal case, "exclusion"
does not necessarily equate to "innocence."
Forensic science. The application of a field of science to the facts related
to criminal and civil litigation.
Gene. A segment of a DNA molecule that is the biological unit of heredity
and transmitted from parent to progeny.
Genotype. The genetic makeup of an organism, as distinguished from its physical
appearance or phenotype.
Inclusion. A DNA test result indicating that an individual is not excluded
as the source of the DNA evidence. In the context of a criminal case, "inclusion"
does not necessarily equate to "guilt."
Inconclusive. The determination made following assessment of DNA profile
results that, due to a limited amount of information present (e.g., mixture
of profiles, insufficient DNA), prevents a conclusive comparison of profiles.
Marker. A gene with a known location on a chromosome and a clear-cut phenotype
(physical appearance or observable properties) that is used as a point of
reference when mapping another locus (physical position on a chromosome).
Polymerase Chain Reaction (PCR). A technique used in the process of DNA
Restriction Fragment Length Polymorphism (RFLP). A technique used in the
process of DNA profiling.
Secretor. A person who secretes the ABH antigens of the ABO blood group
in saliva and other body fluids.
Serologist. A forensic scientist who specializes in biological fluid analysis.