DNA glossary for family history

191e07ca-5617-4d57-8b3b-71996474a7ee

30 January 2025
|
DNA Glossary Learn the scientific and genealogy terms to help you with your DNA research
DNA testing has revolutionised family history, but understanding the results and scientific terms can be a challenge. Get to grips with genetic genealogy with our DNA glossary, written especially for anyone using DNA for family history.

DNA Glossary

DNA has a language of its own, and it’s one you might not be familiar with. It’s worth getting to grips with some of the most commonly used words and terms—some are scientific, while others have evolved specifically within the genealogy community.

Get started here and discover all that DNA tests can offer for your family history research.

  • Admixture: The technical term for an ‘ethnicity report.’ Admixture refers to our geographic origins as interpreted by our DNA.
  • Allele: A specific form of a gene. Our genes can lead to various traits, and the allele determines the outcome, such as having brown eyes.
  • Autosomal DNA (atDNA): DNA inherited from both parents, containing genetic information from all ancestral lines. Used in most consumer DNA tests.
  • Base Pair (bp): A ‘rung’ on the DNA ladder, consisting of chemical pairs: adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C).
  • Centimorgan (cM): A unit for measuring genetic linkage. The more centimorgans shared with a DNA match, the closer the relationship.
  • Chromosome: A structure in cells that contains DNA. Humans have 23 pairs of chromosomes (46 total), including one pair of sex chromosomes.
  • Chromosome Browser: A tool showing which chromosome segments you and a DNA match share. Available on platforms like 23andMe, MyHeritage, and Family Tree DNA.
  • Crossover (Recombination): The process where DNA from both parents mixes during reproduction, creating unique genetic combinations.
  • DNA (Deoxyribonucleic Acid): The molecule that carries genetic instructions for growth, development, and inheritance.
  • DNA Match: A person who shares DNA with you, indicating a genetic relationship. Matches are ranked by the amount of shared DNA (measured in centimorgans).
  • DNA Segment: A portion of DNA shared between two people, helping determine the degree of relatedness.
  • Double Helix: The spiral structure of DNA, consisting of two strands wound around each other.
  • Full Sibling: A sibling who shares both biological parents, typically sharing around 50% of DNA.
  • Genetic Genealogy: The use of DNA testing to trace ancestry and confirm family relationships.
  • Genome: The complete set of DNA in an organism.
  • Haplogroup: A genetic population group sharing a common ancestor. Males can be assigned to two haplogroups (paternal and maternal lines), while females are assigned only a maternal haplogroup.
  • Mitochondrial DNA (mtDNA): DNA passed exclusively from the mother to all her children. Used to trace maternal ancestry.
  • Paternal Lineage: Ancestry traced through the father’s line, often using Y-DNA testing.
  • Pedigree Collapse: When an ancestor appears more than once in a family tree due to relatives marrying within the same lineage, causing repeated DNA inheritance.
  • Phenotype: The physical expression of genetic traits, such as eye color or hair type.
  • Shared DNA: The amount of genetic material two individuals have in common, used to determine relationships.
  • Single Nucleotide Polymorphism (SNP): A variation at a single position in the DNA sequence, often used in ancestry and health testing.
  • Sibling DNA Match: A comparison showing shared genetic material between siblings.
  • STR (Short Tandem Repeat): A type of DNA sequence used in forensic and Y-DNA testing.
  • ThruLines (AncestryDNA Feature): A tool that suggests possible common ancestors based on DNA matches and family trees.
  • Triangulation: The process of confirming a shared ancestor by comparing DNA segments among multiple relatives.
  • X-DNA: DNA inherited differently based on gender. Males inherit one X chromosome from their mother, while females inherit one X from each parent.
  • Y-DNA: DNA passed exclusively from father to son, used to trace paternal ancestry and surnames.