Genetic genealogy terms and definitions compiled and designed to be as simple and easy to understand as possible.  Additional and more technical definitions are available on several other glossary websites.  Terms and definitions are bookmarked to assist comprehension. 

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Administrator - Also known as a 'Project Administrator', 'Group Project Administrator', 'Project Manager', 'Coordinator' and 'Co-Coordinator'.  A volunteer who establishes a DNA study with one or multiple commercial DNA testing companies.

Admixture DNA - The non-gender chromosomes that mix or recombine. Also known as autosomal DNA.

Allele - (pronounced UH-leel) - Used in genetic genealogy in reference to the scientific result for a marker.

Ancestral haplotype - The haplotype of a MRCA deduced by comparing descendants' haplotypes and eliminating mutations.  A minimum of three lines, as distantly related as possible, is recommended for deducing the ancestral haplotype.

Ancestral state - Refers to the state of a SNP that has mutated and is shared by the most people.  Example:  A negative result on a SNP means it is ancestral, a positive result means it is derived.

atDNA - Acronym for Autosomal DNA.

Autosomal DNA - The DNA of non-sex-determining chromosomes that mix or recombine. Also known as admixture DNA.

Anthrogenealogy - A term coined by Family Tree DNA combining the words 'anthro' and 'genealogy' in reference to utilizing DNA to trace one's heritage far beyond recorded documentation. 


Bikini haplotypes - Minimal haplotype data, i.e.: six markers


Coalescence age - The merging of genetic lineages backwards in time to the most recent common ancestor (MRCA)

CODIS - Acronym for Combined DNA Index System - The FBI's autosomal DNA database for profiles of criminal offenders.  

Convergence - When a haplotype mutates enough to appear to be of another haplogroup than it actually is.  The only way to confirm the correct haplogroup designation is through SNP confirmation.

CRS - Acronym for Cambridge Reference Sequence. The first mitochondrial DNA to be fully sequenced at Cambridge University in 1981.  The anonymous donor of the CRS was haplogroup 'H'.  Mitochondrial results are determined based upon where the results differ from the CRS.


Derived state - Refers to the state of a SNP that has mutated, usually in one man, from the ancestral state and created a new haplogroup or sub-clade of a haplogroup.  A positive SNP result is derived, a negative SNP result is ancestral

DNAF - Acronym for DNA-Fingerprint - a commercial DNA testing company. (Acquired by Family Tree DNA in 2006).

DNAH - Acronym for DNA Heritage - a commercial DNA testing company.

DNA-NEWBIE - A DNA-Newbie is someone who is new to the field of genetic genealogy.  It is also the name of a Yahoo mailing list forum sponsored by the International Society of Genetic Genealogy. http://groups.yahoo.com/group/DNA-NEWBIE/

DYS - Acronym for DNA Y-chromosome Segment - The assigned number of a marker on a segment of the Y-chromosome.  Example: DYS# 393


EA - Acronym for EthnoAncestry - a commercial DNA testing company.


FGS - Acronym for Full Genomic Sequence - Usually used in referring to a full mitochondrial sequence test comprising all 16,569 base pairs.

FST - Acronym for Full Sequence Test - Again, usually used in referring to a full sequence mitochondrial test. See FGS.

FTDNA - Acronym for Family Tree DNA - a commercial DNA testing company.

FTDNATiP - Acronym for Family Tree DNA Time Predictor - A program created to calculate the time to the MRCA using mutation rates specific to each marker. 


GAP - Acronym for the Group Administrator Page - This is a webpage in which a DNA Project Administrator utilizes functions such as creating a public website, generating a FTDNATiP report, etc. to assist project participants in coordinating results. 

GEDCOM - Acronym for Genealogical Data Communications - A plain text program created for exchanging genealogical data between different genealogical programs.  Family Tree DNA's 'My FTDNA' page, Y-Search and Mitosearch all contain a feature to upload a GEDCOM for pedigree comparisons to matches.

Genetic Genealogy - The latest tool for genealogists utilizing DNA to aid genealogical research.

Genographic Project - (pronounced GENE-o-graphic) - A five-year scientific genetics project launched in 2005 to study and map human migratory patterns.  Along with testing indigenous populations, the project offers a 12-marker Y-chromosome or HVR1 mtDNA test for public participation with a portion of the proceeds benefiting the indigenous communities.  The project is sponsored by National Geographic, IBM and the Waitt Foundation.  Genographic participants have the option to join Family Tree DNA's database once their DNA results are in.


Haplogroup - A group of similar haplotypes that share a common ancestor with a SNP mutation.  Because a haplogroup consists of similar haplotypes, this is what makes it possible to predict a haplogroup.  A SNP test confirms a haplogroup.  Haplogroups are assigned letters of the alphabet, and refinements consist of additional number and letter combinations, Example: R1b1. Y-chromosome and mitochondrial DNA haplogroups have different haplogroup designations.  Haplogroups pertain to your deep ancestral origins dating back thousands of years.  

Haplotype - The term for the set of numbers that consists of your Y-chromosome or mitochondrial DNA results.  Haplotypes are also known as signatures.

HIR - Acronym for Half Identical Region - Coined by Leon Kull, HIR means that (at least) half of your genotype matches (at least) half of another person's genotype.  Usually used in reference to the blue segments of matching DNA on 23andMe's Family Inheritance diagram.

HVR - Acronym for Hyper Variable Region - The sections of non-coding mitochondrial DNA that are used for genealogical DNA testing.


Acronym for Identical by Descent - The concept that the same segment was inherited by two people through a common ancestor. 

- Acronym for the International Society of Genetic Genealogy, a free society founded in 2005 for the promotion and education of genetic genealogy.


Junk DNA - Slang term usually used in referring to the non-coding region of DNA on the Y-chromosome.  For more about: http://www.psrast.org/junkdna.htm

JoGG - The Journal of Genetic Genealogy - An online journal published quarterly with articles and features pertaining to genetic genealogy and anthrogenealogy.


MSY - Acronym for Male Specific Y - See: NRY

Marker - A specific place on a chromosome with two or more forms, called alleles, the inheritance of which can be followed from one generation to the next.  In genetic genealogy, this refers to non-coding Y-chromosome DNA. Numbers designate the individual DNA segments. Example: 393=13.  This means at marker #393, your allele value is 13.  

Mitochondrial DNA - Energy releasing organelles located in the cytoplasm of cells, which contain their own DNA.  Mitochondrial DNA is passed from mother to child, but only females continue to pass on their maternal mitochondria to their children. 

Mitosearch - A free public database sponsored by Family Tree DNA where mitochondrial DNA results from any testing facility may be uploaded and compared.

MRCA - Acronym for Most Recent Common Ancestor.  The most recent ancestor from which a group of individuals share descent from.

mtDNA - Acronym for mitochondrial DNA.

Mutation - A change in the DNA that occurs spontaneously.  Mutation is a scientific term that often connotes a negative connotation as a result of 1950's 'B' movies, but in genetic genealogy, mutations are utilized for distinguishing different ancestral lines.  Mutations can also occur due to environmental factors, such as exposure to radiation.


Non-coding DNA - Also referred to as 'junk DNA,' non-coding DNA is not part of an active gene that contains a code for making a protein.  Recent evidence shows that at least some non-coding DNA is involved in biological processes such as regulation of gene expression and chemical signaling among cells.  All testing for genealogical purposes is done on non-coding DNA, which makes up nearly 98% of human DNA

NRY - Acronym for Non-Recombining Y - The section of the Y-chromosome that is passed from father to son on down the paternal line.  While it does not recombine, it does have mutations over time.

Nuclear DNA - DNA of chromosomes found in the nucleus of the cell.

Null - A null is a value of zero on a marker.  Nulls can occur due to missing genetic material on a marker, or a SNP can sometimes cause a null result.  Several YSTR markers have been identified in certain families to have null results: 439, 448


OA - Acronym for Oxford Ancestors - a commercial DNA testing company.

Organelle - A cell structure with specialized functions.


Palindrome - A double-stranded DNA segment in which the sequence of one strand is in the reverse order to the other strand.  Example: DYS464X where a family line in R1b1c has cccc or ccgg instead of the usual cccg pattern.

Phylo-tree - Shortened term for Phylogenetic Tree - Most often used in reference to the available online diagrams connecting all Y-chromosome haplogroups.  This term is also applied to DNA project diagrams created by Project Administrators utilizing specialized software.

Proxy - Usually used in reference to the contact person for a DNA test.  Example: A female who has tested a male relative.


RAO - Acronym for Recent Ancestral Origins (formerly known as REO - Recent Ethnic Origins)
The number of matches you have in Family Tree DNA's database as specified by country or region.  To access the RAO, Family Tree DNA clients need to click the tab on their "My FTDNA" page.

recLOH - Acronym for Recombinant Loss of Heterozygosity - When a section of DNA on a marker is missing, that marker is sometimes repaired by another marker filling in the missing DNA with its own material. This is referred to as a "recLOH event" and is usually observed with multi-copy markers like 385a and 385b, and is also common in the 464 set.  The recLOH event causes the allele values to match 11-11 instead of the more common, 11-14 that you see in R1b.  For more about: Recombinational Loss of Heterozygosity (recLOH)

RG - Acronym for Relative Genetics - a commercial DNA testing company. (Acquired by Ancestry.com/The Generations Network in Summer 2007).


SMGF - Acronym for Sorensen Molecular Genealogy Foundation.  Established by James Sorensen as a scientific genealogical DNA database, participants submit a DNA sample along with a four generation pedigree chart.  While participation is free, SMGF does not send participants their results.  However, many participants are able to "find" themselves in the online results database by matching up their pedigrees.  Currently, only Y-chromosome results appear in the database, and the current wait time for results to appear is between nine months to over two years.

SNP - (pronounced SNIP) - Acronym for Single Nucleotide Polymorphism.  A SNP test confirms your haplogroup by determining if a SNP has mutated from its derived or ancestral state.  A SNP is usually found on a different area of the Y-chromosome than where the YSTR markers are.  Sometimes, a SNP may cause a null result on a marker.

STR - Acronym for Short Tandem Repeat - See: YSTR

Sub-clade - Referring to a "branch" farther down the phylogenetic tree.  Example: H3 -> '3' is a sub-clade of mitochondrial haplogroup 'H'.  R1b -> '1b' is a sub-clade of Y-chromosome haplogroup 'R'.  Sub-clade testing is also referred to as deep clade testing.


TG - Acronym for Trace Genetics - a commercial DNA testing company.

Triangulation - A method of determining the DNA haplotype of an ancestor using the DNA results of direct line descendants.


Whit's Predictor - The commonly applied nickname to the "Y-Haplogroup Predictor" created by Whit Athey.  Enter Y-chromosome markers into the predictor and it will display percentages for matches to various haplogroups.


X-chromosome - The female sex chromosome, if a child receives one X from the father and one X from the mother, the child's gender is female.


Y-chromosome - The male sex chromosome.  In other words, only males have a Y-chromosome, which they receive from their father, who received it from his father, and so on.  This transmission of the Y-chromosome down the male line is why it is useful for surname testing to determine if two males share a common ancestor.

Y-Base - A free public database sponsored by DNA Heritage where Y-chromosome DNA results from any testing facility may be uploaded and compared.

Y-Search - A free public database sponsored by Family Tree DNA where Y-chromosome DNA results from any testing facility may be uploaded and compared.  

YSTR - Acronym for Y-chromosome Short Tandem Repeat.  The number of times the sequence of bases repeat that determines the value of the marker.  Example: Thirteen repeats of the same bases equals a value of '13'.

Glossary Websites:

Kerchner's Genetic Genealogy Glossary
National Geographic Genographic Project Genetics Glossary
Family Tree DNA Glossary
Genetics/DNA Glossary - Clan Lindsay
DNA Heritage Glossary
ISOGG's Y-SNP Tree Glossary of Genetics Terms

To purchase a comprehensive published glossary:
Genetic Genealogy DNA Testing Dictionary 


Contribution credits: 
K. Borges, C. Mello, 
P. Goff, E. Krause,
N. Custer, J. Hailman

Copyright 2006-2009
All Rights Reserved
Compiled: 05/17/2006
Last revised: 01/13/2008

Page last updated: 12/07/2009