If you’re exploring DNA testing—whether for relationship verification, immigration, or infidelity concerns—you’ll encounter a variety of scientific terms that might seem overwhelming at first. Understanding these key DNA-related terms can help you make informed decisions about testing and results. Here’s a breakdown of the most important DNA keywords you should know.

DNA (Deoxyribonucleic Acid)

DNA is the genetic material that carries the instructions for the development, functioning, growth, and reproduction of all known living organisms. It is inherited from both biological parents, making it the foundation for DNA testing.

Chromosome

A chromosome is a long DNA molecule that contains many genes. Humans have 23 pairs of chromosomes—one set from each parent—totaling 46 chromosomes in each cell.

Gene

A gene is a specific segment of DNA that contains the instructions for making proteins, which determine characteristics such as eye color, hair type, and even certain genetic predispositions.

Allele

An allele is a variation of a gene. Since individuals inherit one allele from each parent, DNA tests compare alleles to determine biological relationships.

STR (Short Tandem Repeat)

STR analysis is commonly used in relationship and forensic DNA testing. STRs are repeating sequences of DNA that vary between individuals, making them useful for identity and kinship testing.

Locus (Plural: Loci)

A locus is the specific location of a gene or STR marker on a chromosome. In DNA testing, multiple loci are analyzed to determine genetic matches between individuals.

CODIS (Combined DNA Index System)

CODIS is a national DNA database used by law enforcement to store and compare DNA profiles for criminal investigations.

Paternity Index (PI)

The Paternity Index is a statistical value that measures the strength of the genetic match between an alleged father and a child. A higher PI increases the probability of paternity.

Probability of Paternity

Expressed as a percentage, this value represents the likelihood that the tested man is the biological father. In accredited paternity testing, a probability of 99.9% or higher is considered conclusive.

Chain of Custody

A legal process ensuring that DNA samples are collected, handled, and tested in a secure and documented manner. This is required for court-admissible DNA tests.

Buccal Swab

A common, non-invasive method of collecting DNA by swabbing the inside of the cheek. It provides the same accuracy as a blood sample in most DNA tests.

 Legal vs. Non-Legal (At-Home) DNA Test
• Legal DNA Test: Requires strict chain of custody procedures and is admissible in court.
• At-Home DNA Test: Used for personal knowledge without legal validity, as sample collection is not verified by a third party.

Y-STR Testing

A specialized DNA test that analyzes the Y chromosome, which is passed down from father to son. It is useful for tracing paternal lineage and establishing male relationships.

Excluded vs. Non-Excluded

In DNA testing, an individual is either:
• Excluded: The DNA test proves that the alleged relationship is not possible (e.g., an alleged father is not the biological father).
• Non-Excluded: The DNA test provides strong genetic evidence supporting the biological relationship (e.g., the tested man is the likely father).

Secondary Testing

Secondary testing refers to DNA analysis used to determine biological relationships beyond direct paternity. This includes tests for siblingship, grandparentage, or avuncular (aunt/uncle) relationships. It is commonly used when a direct parent-child test is not an option.

Final Thoughts

Understanding these DNA terms can help you navigate the world of genetic testing with confidence. Whether you’re considering DNA testing for personal, legal, or immigration purposes, knowing these key terms will ensure you’re informed every step of the way.

If you have any questions about DNA testing, feel free to reach out to our team at Alliance DNA Laboratory for expert guidance!