Glossary of Ancestry Terms

Learn the Language of DNA Science

DNA science can seem complicated, but it gets considerably simpler when you understand the language! For your convenience, here are explanations for some of the most important terms you're likely to run across during DNA testing for ancestry. So take a few minutes to learn what it all means.

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Accreditation  The process in which a business is reviewed to make sure it is functioning at a level set by respected industry or state organizations. A business may seek and receive accreditation from several accrediting bodies.

Alleles — Different versions of the same gene. Alleles are the ‘genetic switches’ that determine characteristics such as eye color, hair color and height. The chromosomes in a pair carry the same gene in the same places but there may be different versions of the same gene. For any gene, a person may have any combination of two possible alleles - for example they may have two alleles for brown eye color, or one brown one and one blue one.

Ancestral — Something inherited from a person’s ancestors. In genetics, ancestral refers to an inherited characteristic, such as physical appearance as well as certain physical and mental health conditions. Ancestral DNA can be used to find out about a person’s genetic heritage.

Ancestor/Ancestry — A person from whom another is directly descended, typically someone more distant than a grandparent. Your ancestry collectively describes your ancestors.

Autosomal DNA — The DNA found in the autosomes: the 22 chromosomes that do not determine sex. The autosomes carry 90% of your DNA and can be inherited from any of your thousands of ancestors through the ages.

Base Pair — A chemical thread in the DNA, formed by a pair of nitrogenous or base chemicals, which makes up the rungs on the DNA ladder. Each strand of DNA is made up four different base chemicals: adenosine (A), thymine (T), cytosine (C) and guanine (T). These chemicals always pair in the same way: A always pairs with T, and C always pairs with T. Human DNA has about 3 billion bases.

Buccal Swab — A swab taken from the cheek by rubbing the inside of the mouth with a large cotton bud to collect loose cells. Buccal swabbing is a common method of collecting DNA cells for analysis.

Chromosome — A thread-like structure made up of nucleic acids and protein, which is found in the nucleus of animal or plant cells and that carries the genes. There are 23 pairs of chromosomes in each cell of the human body. Chromosomes are inherited from the parent - 23 from the mother and 23 from the father. The 23rd chromosome determines sex - XX for females and XY for males.

DNA — A long twisted ‘helix’ molecule made of deoxyribonucleic acid that holds the body’s unique genetic code. It is made up of four proteins: adenosine (A), thymine (T), cytosine (C) and guanine (T), which form base pairs and which are the basic building blocks of the DNA. The order of these base pairs forms the instructions in the genome. DNA is found in the nucleus of a cell as well as its mitochondria (mtDNA). The nuclear DNA is composed of information inherited from both parents, while the mtDNA in male and female humans is inherited solely from the mother. DNA can be used to determine parentage, as well as a wide range of other information. mtDNA is used to look at the maternal bloodline.

Ethnicity — An ethnic group is a group that has shared characteristics such as culture, language, religion and traditions, and sees itself or is seen by others as a distinct community. It is not necessarily genetic and definitions of what is a distinct ethnicity may vary from place to place.

Family History — The study of how your ancestors lived. The term ‘family history’ is often used interchangeably with ‘genealogy’ but is a much broader exploration of your ancestors’ lives. It encompasses genealogy in that you need to study your ancestral lineage but also considers social history, looking at the area in which your ancestors lived, the jobs they did, what their homes were like and other factors that may have affected their life.

Gene — A gene is the basic unit of information—formed of a distinct sequence of DNA—that determines what characteristics every living creature has. Genes are found on the chromosomes and are inherited from both parents.

Gene Pool — Also referred to as Ancestral Origin, is the collective set of genetic information within a distinct population which does not breed with others from outside of the group. So far, 36 human gene pools around the world have been identified, with each human population made up of a mixture of these gene pools.

Genealogy — The study of a person’s family tree or line of descent. Genealogy uses the written record (birth, marriage, tax and death records), stories passed down through families and increasingly genetic testing.

Genetic Markers — Points of variation in DNA that scientists use to decode and interpret information about the source of the DNA. Genetic markers are ‘bookmarks’, which allow scientists to quickly find out about the genetic characteristics associated with the marker’s location (locus) on the DNA strand.

Genetic Mutation — A permanent change in the DNA sequence that makes up a gene. Mutations can range in size from a single DNA base to a large segment of a chromosome. Genetic mutations can be inherited from a parent or acquired during a person's lifetime. Some genetic changes are very rare while others are common. Genetic changes that occur in more than 1 percent of the population are called polymorphisms. They are common enough to be considered a normal variation in the DNA. Polymorphisms are responsible for many normal differences between people such as eye color, hair color, and blood type.

Genome — An individual’s genetic blueprint: the complete set of genetic instructions needed to make that individual. Every cell with a nucleus contains a complete copy of the genome.

Locus (Loci, pl.) — The specific position of a gene or DNA sequence on a chromosome. Scientists use maps to describe the location and the genetic traits that are determined at those points.

Maternal Line — The lineage that follows your female ancestry through your mother. It traces your mother, your grandmother, great grandmother and so on, and—unless you are male—consists entirely of females.

Mitochondria — A specialized area found within a cell that produces the energy the cell needs to function.

Mitochondrial DNA (mtDNA) — The DNA contained within the mitochondria of cells. The mitochondria are the ‘power stations’ of the cells and produce the energy. Mitochondrial DNA has its own genome distinct from the DNA found in the nucleus. mtDNA in both men and women is inherited from the mother, and is useful for investigating the maternal lineage of a family.

Mutation — See Genetic Mutation

Polymerase Chain Reaction (PCR) — A way of increasing the rate of DNA replication so that unlimited copies can be made from the original DNA sample. It uses DNA polymerase, the enzyme that facilitates DNA replication in nature. It is used in laboratories to multiply the amount of DNA available in a sample for analysis.

Short Tandem Repeat (STR) — A pattern in which several base pairs are repeated in sequences along a strand of DNA. Each person’s genes display unique patterns that are then used to catalog differences in DNA profiles.

Single Nucleotide Polymorphisms (SNP - pronounced ‘snips’) — The most common type of genetic variation among people. Each SNP represents a difference in a single DNA building block or nucleotide. SNPs occur normally throughout a person’s DNA and there are roughly 10 million SNPs in the human genome. Most commonly, these variations are found in the DNA between genes.

X-SV Test — A test that looks at the mitochrondrial DNA (mtDNA) in order to determine whether or not two or more people could be related through the maternal line.

Y-STR Test — A test that looks at the STRs on the Y chromosome in order to determine whether or not two males could be related through paternal bloodlines.

Y-Chromosomal DNA — The DNA that only occurs on the Y chromosome. It is passed down from father to son through the generations and is only inherited by males.