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WikiTree Genetic Genealogy Glossary

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Profile manager: Mindy Silva private message [send private message]
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This is a list of common terms used when applying DNA results to your genealogy research. If you have other terms you would like on the list let me know!

Note: These are just the basic terms used, it is not all inclusive.

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DNA Genealogy Terms

  • atDNA: abbreviation for autosomal DNA
  • autosomal DNA: DNA on a chromosome other than a sex chromosome. Humans normally have 22 pairs of chromosomes.
  • BigY: A trade name for a test offered by Family Tree DNA that examines deep ancestral relationships to identify new SNP's (replaced by the Big Y-500 test)
  • Big Y-500: Trade name for a yDNA test offered by Family Tree DNA that examines deep ancestral relationships to identify new SNP's
  • birth parent: a biological parent (doesn't include adoptions, unknown parentage, etc)
  • centimorgan: a measure of linkage between two positions on a chromosome, abbreviated as cM
  • chromosome: an organizational unit of DNA; humans have 22 pairs of autosomal chromosomes and one pair of sex chromosomes
  • chromosome browser: a visual tool to display matching segments on a chromosome (which part of a chromosome you match a cousin or closer relative on. the more that matches, the closer the relationship)
  • cM: abbreviation for centimorgan
  • cousin bait: a public display of information designed to find genetic cousins and encourage them to communicate (for example, having your kit information on your ancestors pages, or sharing an ancestor on Facebook that has your dna information)
  • DNA: abbreviation for deoxyribonucleic acid; DNA is the chemical that transmits genetic information from one generation to the next
  • DNA Circles: Trade name for a tool at AncestryDNA that identifies groups of DNA testers that most likely descend from a specific ancestor. Note: They're changing how you look at your DNA matches on Ancestry and when you click on a match it shows 'Shared Matches' (other people that most likely descend from the same ancestor).
  • endogamy: the practice of finding matches within the same group, such as a geographic, religious or ethnic group, that can cause cousins to share more DNA than expected for that relationship.
  • false positive: a DNA segment that seems to match between two people but was not inherited from a parent; a statistical anomaly resulting from the fact that some DNA tests cannot assign segments to one parent or the other
  • gd or ged: abbreviation for genetic distance
  • GEDmatch: a website with tools to analyse your dna results
  • gen: on GEDmatch, a number representing how many generations there are between two matches (for example, a gen of 3 indicates the common ancestor may be three generations back)
  • genetic distance: a whole number that indicates the number of mutations that differ between two people that have taken a yDNA or mtDNA test; a genetic distance of zero means an exact match
  • identical-by-chance — a term to describe DNA segments that are identical or nearly identical because of chance events rather than common ancestry (abbreviated IBC)
  • identical-by-descent — a term to describe DNA segments that are identical or nearly identical because they were inherited from a common ancestor (abbreviated IBD)
  • identical-by-state — a term to describe DNA segments that are identical or nearly identical; although technically the term does not imply why the segments are identical, it is commonly used to mean identical-by-chance (abbreviated IBS)
  • MRCA: Most Recent Common Ancestor; the closest ancestor to you that both you and a cousin have in common (for example, you have different parents and grandparents but share a great-grandparent. That is you MRCA even if that ancestor is three generations away for you, and four generations away from your cousin).
  • mtDNA: mitochondrial DNA; this is DNA that is usually inherited from your mother (it can be passed down to a son, but that son can't pass mtDNA to his children). Testing for you mtDNA can help you look further back into your 'tree' on your mother's line only.
  • non-parental event (also non-paternity event or misattributed parentage event) - when a presumed father is not the biological father; occasionally used for a misattributed mother (an adopted or step-mother).
  • search angel — an experienced volunteer who helps others find biological family, usually in cases of adoption or other unknown parentage
  • segment — a length of DNA that was inherited intact from an ancestor
  • sex chromosome — a chromosome that determines biological sex; a person normally has either two copies of the X chromosome and is female or has one X and one Y chromosome and is male
  • triangulation — a technique in which three or more people who all share the same segment of DNA compare family trees to infer which common ancestor contributed that segment. On WikiTree you would use the information from you and two cousins (third cousins or greater) that you compared on a site such as GEDmatch to prove you all descend from a specific ancestor.
  • X chromosome: a chromosome that determines the sex of all people; women usually have two copies of the X chromosome, while males have one X and one Y chromosome.
  • Y chromosome: a chromosome found in men that determines their sex

DNA Help Pages

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Comments: 1

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Hi, Mindy. Just stumbled across this page. I assume, then, that the previous "DNA Project Resources Page" ( has been deprecated and should probably be removed or hidden? It used to be linked directly from the DNA Project's main page, but it hasn't been updated since 2017, and had some errors/omissions even then.

Speaking of, new terminology is added to the field fairly frequently, and I'm not certain of the value of undertaking the difficult task of maintaining a glossary like this. Even I wouldn't want to do it and I'm just slightly OCD-encyclopedic on the subject. What I had proposed several years ago is simply linking to the glossary at ISOGG (, which is maintained by a group of specialist volunteers. Not all terms pertinent to WikiTree will ever be included there (things like Cousin Bait or Search Angel, for example), but you stand a better chance of finding accurate and current glossary entries. As is, there are a few accuracy problems with some items on this page and I'd hate for any WikiTreers to be misinformed, even if only by a nuance.

For even attempting it, though, you have a round of applause from me!  :-)

posted by Edison Williams

Categories: Silva-1055