Glossary of Genetic Testing Terms
Allele
One of several alternate forms of a gene occupying a particular location in a chromosome.
Bases
The chemical units (adenine, thymine, guanine and cytosine) in a DNA molecule that constitutes the genetic code.
Buccal Sample
An oral, mouth or cheek sample obtained using a cotton or sponge swab. A gentle, non-invasive approach to sample collection that collects cells from the inside surface of the cheek for use in DNA analysis.
Chromosome
The location of hereditary (genetic) material within a cell. Genes are found arranged in a linear sequence along chromosomes. Humans have 23 pairs of chromosomes. One of each pair is inherited from the mother and the other from the father.
DNA
DNA ("deoxyribonucleic acid") is the substance human beings (and all other higher forms of life) use to store the information needed to conduct the process of life. It also is the material that carries the genes that we pass to our children.
Electrophoresis
A technique for arranging biological particles across a gel medium by exposing them to an electric field.
Gene
The portion of a DNA molecule that contains the basic functional unit of heredity.
Genetic Marker
Any character that acts as a signpost or signal of the presence or location of a gene or heredity characteristic in an individual in a population.
Locus
The position on a chromosome at which the gene for a particular trait resides.
Paternity
The state of being a father.
Maternity
The state of being a mother.
Paternity Index (PI)
Summarizes the genetic evidence of a test, and reflects how common a shared allele is in the population. If the PI is close to 1, the allele is fairly common. The larger the PI, the more significant the match. Specifically, the PI is the ratio between the likelihood that the tested man is the source of the paternal allele and the likelihood that a random person is the source.
Phlebotomist (Technician)
An individual who is trained and qualified to collect buccal samples and/or to draw blood samples for DNA paternity tests.
Polymerase Chain Reaction (PCR)
A method of DNA analysis that amplifies a specific DNA (gene) region allowing rapid DNA analysis.
Polymorphism
A naturally occurring or induced variation in the sequence of genetic information on a segment of DNA.
Power of Exclusion
The ability of a genetic marker to exclude a falsely accused man of paternity.
Probability of Exclusion
The average probability that a single genetic system will exclude a non-father from paternity prior to testing.
Probability of Paternity
Summarizes the genetic evidence (paternity index) and non-genetic evidence (prior probability, assigned as neutral, 0.5). The probability of paternity is the probability that the tested man is the biological father of the child, expressed as a percentage. Many states accept 99.0% as indicative of paternity; some states required 99.5% to 99.9%.
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