A Genetic Genealogy Glossary

This glossary is a work in progress. Feel free to suggest additions or corrections.
Words in italics are defined elsewhere in the glossary.

23andMe— a personal genomics and biotechnology company that offers an autosomal DNA test with haplogroup assignment(s) and ethnicity estimates; health reports and relative matching are optional

3/4 siblings — half siblings who share one parent and whose other parents are themselves full siblings; 3/4 siblings share less DNA on average than full siblings but more than half siblings and they have fully identical regions; the term apparently originated in horse breeding

529andYou — an extension for the Chrome internet browser that collects DNA segment information from 23andMe and stores it in a local file; the name is a play on 23andMe (529 is the square of 23)

A


adenine (abbr. A) — one of the four nucleotides that make up DNA; the others are cytosine (C), guanine (G), and thymine (T)

admixture — interbreeding between two populations that had previously been separate; in genetic genealogy, the term is often used to mean the percentages of a genome that can be assigned to given populations; see also ethnicity

aDNA — abbreviation for ancient DNA

allele — a variant form of a gene; for example, the alleles IA, IB, and i are all variants of the gene for ABO blood type

allosome — biological term for sex chromosome

amino acid — a type of molecule that forms proteins

Ancestry.com — a genealogy company that hosts family trees and offers subscription access to genealogical records (also called Ancestry)

Ancestry Composition — name for the admixture report at 23andMe

AncestryDNA — a genetic genealogy testing company that offers autosomal DNA tests with ethnicity estimates and relative matching; a subsidiary of Ancestry LLC

ancient DNA (abbr. aDNA) — DNA that has been recovered from ancient samples

Are Your Parents Related? (abbr. AYPR) — a tool at GEDmatch that measures runs of homozygosity; it can indicate whether a DNA tester is the product of incest or recent pedigree collapse

atDNA — abbreviation for autosomal DNA

AutoClusters — trade name for a visual chart showing groups of shared matches; available at Genetic Affairs, MyHeritage, and GEDmatch; AutoClusters were inspired by the Leeds method

autosomal DNA (abbr. atDNA) — DNA on a chromosome other than a sex chromosome; humans normally have 22 pairs of autosomal chromosomes

avuncular — referring to the relationship between an aunt/uncle and their niece/nephew; see also nibling

AYPR — abbreviation for the Are Your Parents Related? tool at GEDmatch

B


base pair (abbr. bp)— a unit of DNA made of two nucleotides joined by weak chemical bonds; adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G)

Bayesian analysis — a statistical method that allows an estimated of probability to be improved as more data become available; in phylogenetics, Bayesian analysis is sometimes used as shorthand for maximum-likelihood-based Markov-chain Monte Carlo methods

Big Y — trade name for a yDNA test offered by FamilyTreeDNA that uses next-generation technology to sequence approximately 12 million base pairs of the Y chromosome; used to examine “deep” ancestral relationships and to identify new haplogroup-defining SNPs; this test has been replaced by the Big Y-700 test

Big Y-500 — trade name for a yDNA test offered by FamilyTreeDNA that uses next-generation technology to sequence approximately 12 million base pairs of the Y chromosome as well as 500 or more STR markers; used to examine “deep” ancestral relationships and to identify new haplogroup-defining SNPs; this test has been replaced by the Big Y-700 test

Big Y-700 — trade name for a yDNA test offered by FamilyTreeDNA that uses next-generation technology to sequence approximately 12 million base pairs of the Y chromosome as well as 500 or more STR markers; used to examine “deep” ancestral relationships and to identify new haplogroup-defining SNPs

birth parent (also birth mother, birth father) — a biological parent; used to distinguish a biological parent from a social parent when the two are not the same, e.g., in adoption, unknown parentage, or misattributed parentage; see also social parent

Bode Technology — a DNA forensics company that engages in forensic genetic genealogy

Borland Genetics — an autosomal matching database with emphasis on DNA profiles of deceased individuals, linked to a set of DNA reconstruction tools for creating kits representing deceased ancestors

bp — abbreviation for base pair; see also Mbp and kbp

C


centimorgan (abbr. cM) — a measure of genetic linkage between two positions along a chromosome; a segment of DNA that is 100 cM long will undergo an average of one crossing over event per generation

centromere — the region of a chromosome where the two duplicated copies attach to one another during cell division; autosomal DNA tests for genealogy do not test SNPs in the centromere region, but crossing over there is rare, so a segment that seems to span the centromere can be safely considered a single, continuous segment

Charting Companion — a software program that creates family charts, including McGuire charts, from family tree files

chromosome — an organizational unit of DNA; normal humans have 22 pairs of autosomal chromosomes and one pair of sex chromosomes; the word literally means colored body, based on how they look under a microscope when stained

chromosome browser — a visual tool that displays the physical locations of matching autosomal DNA segments overlaid on a cartoon of the DNA tester’s own autosomal and/or X chromosomes

Chromosome Maps — a tool to depict shared DNA segments and assign them to the ancestors from which they originated; part of the DNA Painter suite of tools

CLM — abbreviation for the Collins Leeds Method

cluster — see clustering

clustering — a visual way of organizing autosomal DNA matches in a spreadsheet format; matches are listed in order down the first row and again across top column, and the intersecting cell is colored when two matches also match one another; a colored cluster may represents one ancestral branch of a family tree

cM — abbreviation for centimorgan

cM Estimator — a tool on the DNA Painter website that estimates the centimorgan value of a segment based on the start and stop positions; see this post for more information

code — verb indicating that a section of DNA gives instructions for making a protein, e.g. TAS2RR38 codes for a bitter taste receptor

coding DNA — a sequence of DNA that provides the genetic information to make a protein; see also non-coding DNA, junk DNA

Collins Leeds Method — trade name for a visual chart showing groups of shared matches; available through the DNAGedcom Client; inspired by the Leeds method

common ancestor — an ancestor shared by two or more people; for example, your grandparents are common ancestors between you and a first cousin

common ancestor hint —a tool at AncestryDNA that identifies potential ancestors shared by a tester and their DNA matches

cousin bait — a public display of information designed to find genetic cousins and encourage them to communicate (see also cousin fishing)

cousin fishing — the process finding genetic cousins and encouraging them to communicate; the term cousin fishing is used loosely to describe methods such as autosomal DNA testing, posting a public family tree, blogging, etc.; see also cousin bait

crossing over — the exchange of DNA between paired copies of a chromosome during the first cell division of meiosis; crossing over causes shared segments to decrease in size over generational time

Custom Groups — a feature at AncestryDNA that allows the user to create custom, color-coded filters for their DNA matches; see this post for more information

cytosine (abbr. C) — one of the four nucleotides that make up DNA; the others are adenine (A), guanine (G), and thymine (T)

D


DD — abbreviation for DNA Detectives; as part of a GEDmatch user name, DD indicates that the tester is either searching for biological family or willing to help someone searching

deletion — a type of DNA mutation caused by the removal of one or more nucleotides

deoxyribonucleic acid (abbr. DNA) — chemical that transmits genetic information from one generation to the next

DNA — abbreviation for deoxyribonucleic acid

DNA Circles — trade name for a defunct tool at AncestryDNA that identified groups of DNA testers who were probably descended from a specific ancestor

DNA Day — commemorates the day (April 25, 1953) when the paper describing the structure of DNA was published; DNA testing companies may discount prices around this time

DNA Detectives — may refer to the media consulting company or its offshoot Facebook support group for individuals using DNA test results to seek biological family

DNA Doe Project — a non-profit organization that uses genetic genealogy to identify unknown remains, known as Does

DNA Relatives — trade name for the relative matching tool at 23andMe

DNA Solves — a forensic genetic genealogy matching database

DNAGedcom — a website with tools to assist with genetic genealogy analyses

DNAGedcom Client — a software program that collects autosomal DNA data from the DNA match sites and provides analytical tools; known for the Collins Leeds Method

DNA Land — a website with tools to assist with genetic genealogy analyses and to contribute to biomedical research

DNA Painter — a website with tools to assist with genetic genealogy analyses, best known for its Chromosome Maps, Shared cM Project Tool, and What Are the Odds?

Dodecad — an admixture (ethnicity) calculator at GEDmatch focused on European, Asian, and North African populations

Doe — (also John Doe, Jane Doe) an unidentified person or remains of such a person

dominant— of an allele, the version that is expressed when two versions are present; see also recessive, incomplete dominance

downstream — the portion of a haplogroup tree descended from the node where a given SNP first appears

E


endogamy — the practice of finding mates within the same group, such as a religious, ethnic, or geographic group; endogamy can cause relatives to share more DNA than expected given the relationship; an extreme form of pedigree collapse, and not to be confused with incest

Ethiohelix — an admixture (ethnicity) calculator at GEDmatch focused on African populations, especially East African and Ethiopian ones

ethnicity — as used in genetic genealogy, the proportions of one’s genetic makeup that can be assigned to different ancestral populations; see also admixture

Ethnicity Estimate — name for the admixture report at AncestryDNA

Eurogenes — an admixture (ethnicity) calculator at GEDmatch focused on European populations

evolution — a change in allele frequencies in a population over generational time

excess IBD — a disproportionate number of DNA matches at a given spot in the genome, usually a small segment of DNA; regions of excess IBD are widespread in a population and are usually not indicators of recent genealogical relationships; also called pile-ups

Exploring Family Trees — a website with tools for visualizing family trees

F


false match — see false positive

false positive — a DNA segment that seems to match between two people but that was not inherited from a parent; false positives are statistical anomalies resulting from the fact that microarray DNA tests cannot assign alleles to one parent to the other

Family Finder — trade name for the autosomal DNA test offered by FamilyTreeDNA

FamilySearch — a genealogy organization that hosts family trees and offers free access to genealogical records

FamilyTreeDNA (abbr. FTDNA) — a genetic genealogy testing company and that offers autosomal, mitochondrial, and yDNA tests to the public and forensic services to law enforcement; their autosomal test includes a ethnicity estimates, and all of their tests match users to DNA relatives

FGGS — abbreviation for forensic genetic genealogy search

FIR — abbreviation for fully identical region

fishing — see cousin fishing

forensic genetic genealogy search (abbr. FGG, FGGS; also investigative genetic genealogy)the use of genetic genealogy techniques to identify human samples, either from a crime scene or unidentified remains; FamilyTreeDNA and GEDmatch both sell access to their databases to law enforcement and Doe investigators for this purpose

Fox spreadsheet — an Excel spreadsheet with macros to automate some steps in visual phasing; named for its programmer

FTDNA — an abbreviation for the company FamilyTreeDNA

full siblings — individuals who share both parents; they share roughly half their DNA, some of which is found in fully identical regions

fully identical region (abbr. FIR) — a segment of DNA in which two people share identical SNPs on both copies of that chromosome, meaning they each inherited that segment from both parents

G


gamete — a sex cell (egg or sperm)

g.d. or gd — abbreviation for genetic distance

GEDmatch — a website with tools to assist with genetic genealogy analyses and to aid forensic investigations

GEDMatch Pro — a portal to the GEDmatch database used by forensic investigators

gen — at GEDmatch, a number representing the typical number of generations separating two DNA matches sharing a given amount of DNA; for example, a gen of 2 implies that the common ancestor is two generations back at the grandparent level

gene — a unit of DNA that influences an individual’s characteristics; the various forms of a given gene are called alleles; for example, the ABO gene for blood types has three alleles, IA, IB, and i

Gene by Gene — the parent company of FamilyTreeDNA; it merged with the Australian pharmacogenetics company myDNA in January 2021

Genealogical DNA Analysis Tool (abbr. GDAT) — a software program for managing DNA test results and chromosome segment data; superceded Genome Mate Pro

Genetic Affairs — a website for analyzing autosomal DNA match data; most widely known for the AutoClusters tool

Genetic Communities — trade name for a tool at AncestryDNA that can assign DNA testers to groups based on their genetic connections within each group; similar to Genetic Groups at MyHeritage; see this post for more information

genetic distance (abbr. g.d. or gd) — a whole number that indicates the number of mutations that differ between two people who have taken the same yDNA or mtDNA test; a genetic distance of zero means an exact match

genetic genealogy — a discipline in which DNA tests results are used to assist genealogy research

Genetic Groups — a tool at MyHeritage that can assign DNA testers to groups based on their genetic connections within each group; similar to Genetic Communities at AncestryDNA

genetics — the field of biology that studies genetic inheritance, mutation, gene expression, and genetic variation; see also population genetics

genome — all of the genetic material in a species, individual, or organelle (e.g., human genome, nuclear genome, mitochondrial genome)

Genome Mate Pro (abbr. GMP) — an obsolete software program for managing DNA test results; replaced by Genealogical DNA Analysis Tool

GedrosiaDNA — an admixture (ethnicity) calculator at GEDmatch focused on Eurasian and Sub-Saharan populations

GMP — abbreviation for Genome Mate Pro

Golden State Killer (abbr. GSK) — American serial rapist, serial murderer, and former police officer named Joseph James DeAngelo who was active in the 1970s and 1980s in California; he was identified in 2018 using forensic genetic genealogy with the collaboration of FamilyTreeDNA and using the GEDmatch and MyHeritage databases without their knowledge

GSK — abbreviation for the Golden State Killer

guanine (abbr. G) — one of the four nucleotides that make up DNA; the others are adenine (A), cytosine (C), and thymine (T)

GWAS — abbreviation for genome-wide association study

H


half identical region (abbr. FIR) — a segment of DNA in which two people share identical SNPs on one of two copies of that chromosome, meaning they each inherited that segment from one parent

half siblings — individuals who share one parent but not both parents

haplogroup — a group of similar haplotypes that are related by common descent and usually defined by a SNP mutation

haplotree — a visual depiction of the phylogenetic (evolutionary) relationships among haplogroups

haplotype — the sequence of DNA that is inherited intact from a single parent; a haplotype can contain multiple genes and non-coding regions; most commonly used to describe Y-chromosome DNA and mitochondrial DNA

HarappaWorld — an admixture (ethnicity) calculator at GEDmatch focused on Southeast Asian populations

high ROH — of an autosomal DNA test, having uncommonly high amounts of runs of homozygosity indicating that the parents were closely related

HIR — abbreviation for half identical region

hypothesis — a possible answer to a question; an hypothesis need not be true to be valid, but it must be testable; we use evidence to decide which of competing hypotheses is correct

I


IBC — abbreviation for identical-by-chance or identity-by-chance

IBD — abbreviation for identical-by-descent or identity-by-descent

IBS — abbreviation for identical-by-state or identity-by-state

ICW — an abbreviation for in common with

identical-by-chance (abbr. IBC; also identity-by-chance) — a term to describe DNA segments that are identical or nearly identical because of chance events rather than common ancestry

identical-by-descent (abbr. IBD; also identity-by-descent) — a term to describe DNA segments that are identical or nearly identical because they were inherited from a common ancestor

identical-by-state (abbr. IBS; also identity-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

IGG — abbreviation for investigative genetic genealogy

in common with (abbr. ICW; also relatives in common, shared matches) — a term to describe DNA matches to a tester who also share DNA with one another

incest — sexual intercourse between two closely related individuals, typically closer than first cousins; incest can complicate genealogical DNA analysis for a child of incest because DNA matches are related more than one way; a form of pedigree collapse, and not to be confused with endogamy

incomplete dominance — of an allele, when different versions each have a partial effect; see also recessive, dominant

indel — a type of DNA mutation caused by the addition or removal of one or more nucleotides; the term is formed by combining the words insertion and deletion

independent assortment — the biological principle that alleles for one gene will be passed on to a child independently of alleles for a different gene; independent assortment causes segments to be passed on randomly to the next generation

informed consent — permission given for an act by someone who has legal authority and who clearly understands the facts, implications, and consequences of the action; in genetic genealogy, informed consent is needed from the tester or a legal representative to participate in scientific research projects

insertion — a type of DNA mutation caused by the addition of one or more nucleotides

International Society of Genetic Genealogy (abbr. ISOGG) — an organization that advocates for and educates about genetic genealogy

investigative genetic genealogy (abbr. IGG) — another term for forensic genetic genealogy

ISOGG — abbreviation for International Society of Genetic Genealogy; may refer to the society’s Facebook group or its wiki

J


junk DNA — a sequence of DNA with no known function; most of the human genome is junk DNA; see also coding DNA, non-coding DNA

K


kbp — abbreviation for kilobase pairs

kilobase pairs (abbr. kbp) — 1,000 base pairs of DNA

L


Leeds method — a method to organize autosomal DNA matches into groups based on shared matches; the Leeds method was the inspiration for automated clustering tools

likelihood — see maximum likelihood

Living DNA — a DNA testing company whose product includes ethnicity estimates, haplogroup assignments, relative matching, and optional wellness reports

M


manager — at some DNA testing companies, a person other than the DNA tester who has authority over the results; a manager is often an active genealogist who has asked other family members to test to help their research; see this post for details specific to AncestryDNA

maximum likelihood (abbr. ML; also likelihood) — an advanced method for estimating phylogenetic trees that incorporates some of the known complexities about how DNA changes over time; see also neighbor joining, maximum parsimony

maximum parsimony (abbr. MP; also parsimony) — a basic method for estimating phylogenetic trees that uses simplified assumptions about how DNA changes over time; see also neighbor joining, maximum likelihood

Mbp — abbreviation for megabase pairs

McGuire chart — a visual representation of shared autosomal DNA amounts among multiple descendants of a common ancestor or couple

MDKA — abbreviation for most distant known ancestor

MDLP Project — an admixture (ethnicity) calculator at GEDmatch focused on global populations

megabase pairs (abbr. Mbp) — 1,000,000 base pairs of DNA

meiosis (plural meioses) — a type of cell division that produces gametes (eggs or sperm); during meiosis, the amount of DNA present in normal body cells is halved

microsatellite — see short tandem repeat

microsatellite mutation — a type of mutation in which a repeating string of nucleotides (called a microsatellite or short tandem repeat) increases or decreases in length

migration — the movement of individuals, groups, or populations from one geographic region to another; this use of the word should not be confused with seasonal movements of some animal species, such as birds

mirroring — a technique used at AncestryDNA to identify where in a DNA match’s tree the probable common ancestor is

misattributed parentage event (abbr. MPE) — a situation in which a presumed parent is not the biological parent; see also non-parental event

mitochondrial DNA (abbr. mtDNA) — DNA found in the mitochondrion; it is made up of about 16,569 base pairs arranged in a circle

mitochondrion (pl. mitochondria) — an organelle in body cells that produces energy; it has its own DNA separate from the nuclear DNA

mitosis — a type of cell division that normally results in two daughter cells with the same genetic makeup; most body cells divide this way

ML — abbreviation for maximum likelihood

most recent common ancestor (abbr. MRCA)— when comparing two (or more) relatives, the most recent shared ancestor in generations to both of them; two relatives may have more than one common ancestor at different generational levels

MP — abbreviation for maximum parsimony

MPE — abbreviation for misattributed parentage event

MRCA — abbreviation for most recent common ancestor

mtDNA — an abbreviation for mitochondrial DNA

mutation — a change in the nucleotide sequence; mutations of most interest to genetic genealogy are point mutations, indels, and microsatellite mutations

myDNA — an Australian pharmacogenetics company that merged with FamilyTreeDNA and its parent company Gene by Gene in January 2021

MyHeritage — a genealogy company that hosts family trees, offers subscription access to genealogical records, and provides autosomal DNA tests

myOrigins — trade name for the admixture report at FamilyTreeDNA

N


NAD — abbreviation for New Ancestor Discoveries; NAD was often used in the singular to refer to a relative suggested by the tool

neighbor joining (abbr. NJ)— a basic method for estimating phylogenetic trees that clusters entities by similarity; neighbor joining is fast but not alway accurate; see also maximum parsimony, maximum likelihood

New Ancestor Discoveries (abbr. NAD) — trade name for a defunct feature offered by AncestryDNA that suggested possible ancestors or relatives who were not already in the tree linked to a given DNA test result; superceded by ThruLines

NGS — abbreviation for next-generation sequencing

nibling — a niece or nephew; sometimes used to refer generally to the aunt/uncle–niece/nephew; see also avuncular

non-coding DNA — a sequence of DNA that does not provide the genetic information to make a protein; non-coding DNA may or may not have a function; most nuclear DNA in humans is non-coding; see also coding DNA, junk DNA

non-parental event (abbr. NPE) — a situation in which a presumed parent is not the biological parent; the term was co-opted from non-paternity event to include either parent being misattributed (see also non-paternity event, misattributed parentage event)

non-paternity event (abbr. NPE) — a situation in which a presumed father is not the biological father (see also non-parental event,  misattributed parentage event)

NPE — abbreviation for non-paternity event or non-parental event; sometimes interpreted to mean “not the parent expected”

nuclear DNA — DNA found in the nucleus of the cell; nuclear DNA includes the autosomes and the sex chromosomes and represents the vast majority of the human genome (see also mitochondrial DNA)

nucleotide —a chemical building block of DNA; the four nucleotides are commonly referred to by their key subunits: adenine (A), cytosine (C), guanine (G), and thymine (T)

nucleus — a compartment in a cell that is encased in a membrane and that contains DNA

O


opt-in — a consent system in which a database user must make an active choice to opt into an activity

opt-out — a system in which database users are set to participate in an activity by default and must take action to opt out

organelle — a compartment within a cell that has a specific function; the two organelles relevant to genetic genealogy are the nucleus (where nuclear DNA is found) and the mitochondrion (where mitochondrial DNA is found)

Othram — a DNA forensics company that engages in forensic genetic genealogy

P


PAR — abbreviation for pseudoautosomal region

Parabon NanoLabs — a DNA therapeutics and forensics company that engages in forensic genetic genealogy

parsimony — see maximum parsimony

pedigree collapse — reproduction between mates who are relatives (e.g., a marriage between second cousins); without collapse, the number of ancestors in a pedigree doubles every generation, but with collapse, some ancestors appear more than once in the pedigree; endogamy is an extreme form of pedigree collapse

phasing — the process of determining which autosomal SNP alleles are associated with other SNP alleles on the same maternal or paternal chromosome; see also trio phasing, statistical phasing, and visual phasing

phylogeny (also phylogenetic tree) — a branching diagram that shows the inferred evolutionary relationships among taxonomic units; the taxonomic units can be species, populations, haplogroups, languages, or other any other entity that has an evolutionary relationship to others

Pike utilities — a suite of free DNA tools created by Memorial University Professor David Pike

pile-up — a layperson term for excess IBD

point mutation — a type of mutation in which one nucleotide is replaced by another

population genetics — a subfield of genetics that concerns genetic variation within and among populations, usually in the context of evolution; see also genetics

private tree — a family tree that is not accessible to others without express permission from the tree’s owner

protein — a molecule made up one or more long chains of amino acids; proteins are the workhorses of the cell and perform many functions

pruning — a outdated method used with AncestryDNA results to identify a shared ancestor in a private tree; see here for a description; this method was rendered obsolete by ThruLines

pseudoautosomal region (abbr. PAR) — a region of DNA where the X and Y chromosomes recombine; the pseudoautosomal region on the short arms of chromosomes X and Y (PAR1) is 2.6 Mbp, and the one on the long arms (PAR2) is 320 kbp

public tree — a family tree that can been viewed by others without express permission from the tree’s owner

PuntDNAL — an admixture (ethnicity) calculator at GEDmatch focused on ancient populations

purine — a chemical class that includes the nucleotides A and G

PWAS — abbreviation for phenome-wide association study

pyrimidine — a chemical class that includes the nucleotides C and T

Q


qualitative trait — a genetic trait that is controlled by one or two genes that can take on only a few discrete values, e.g., ABO blood types

quantitative trait — a genetic trait that is controlled by multiple genes and that can take on a range of values, e.g., height

R


raw data — the results of a laboratory DNA test; the raw data include only the base calls or STR results for the person tested

recessive — of an allele, the version that is not expressed when two versions are present; see also dominant, incomplete dominance

recombination — the exchange of genetic material between homologous chromosomes during meiosis; crossing over (Note: there are other forms of recombination not included in this definition, but they are not generally relevant to genetic genealogy)

recombine — to undergo recombination

relatives in common (also in common with, shared matches) — a term to describe DNA matches to a tester who also share DNA with one another

remove — a term used to describe a generational difference between cousins; once removed refers to one generational difference, twice removed to two, etc.; for example, first cousin once removed describes the relationship between a person and the child of his/her first cousin

ROH — abbreviation for run of homozygosity

run of homozygosity (abbr. ROH) — a segment of a paired chromosome that is identical on both copies of that chromosome, meaning it was inherited from both parents

S


SCP — abbreviation for the Shared cM Project

search angel — an experienced volunteer who helps others find biological family, usually in cases of adoption or other unknown parentage

searchable tree — a private tree at Ancestry.com for which limited information about deceased people may appear to other Ancestry users in search results; useful for unknown parentage searches using DNA

segment — a length of DNA that was inherited intact from an ancestor

sex chromosome (also allosome) — a chromosome that usually determines biological sex; most females have two copies of the X chromosome while most males have one X and one Y chromosome

Shared Ancestor Hint — former trade name for the common ancestor hint tool at AncestryDNA

Shared cM Project (abbr. SCP) — a crowd-sourced project that compiles real-world data on the ranges of shared DNA amounts for known relationships

Shared cM Project Tool — a tool that visualizes possible relationships for a given amount of shared DNA and reports probabilities to gauge which relationship is most likely; part of the DNA Painter suite of tools

shared matches (also in common with, relatives in common) — a term to describe DNA matches to a tester who also share DNA with one another

short tandem repeat (also microsatellite) — a string of 2–5 base pairs that repeat in a DNA sequence, e.g., ATCATCATCATCATC; the number of repeats in an STR can reflect family history; commonly used for yDNA

single-nucleotide polymorphism (abbr. SNP) — a nucleotide position in the genome that is known to vary among individuals because of past point mutations

SMGF — abbreviation for Sorenson Molecular Genealogy Foundation

SNP — abbreviation for single-nucleotide polymorphism (pronounced “snip”)

social parent — a non-biological parent; used to distinguish a biological parent from a non-biological one when the two are not the same, e.g., in adoption, unknown parentage, or misattributed parentage; see also birth parent

SRY gene — the gene that determines maleness in most mammals; usually found on the Y chromosome; see this post for more information

statistical phasing — a method of phasing autosomal DNA results using haplotype frequencies from a reference population rather than parent–child trios; see also phasing, trio phasing

STR — abbreviation for short tandem repeat

T


taxonomic unit — an entity represented in a phylogenetic tree

terms of service (also terms of use) — the legal agreement between a customer and a company, in this case a DNA test taker and the DNA testing service

Theories of Family Relativity — trade name for  feature at MyHeritage that compares and extends family trees to identify potential shared ancestors between two DNA matches; similar to ThruLines

three-quarter siblings — see 3/4 siblings

ThruLines — trade name for a feature at AncestryDNA that compares and extends family trees to identify potential shared ancestors between two DNA matches; similar to Theories of Family Relativity

thymine (abbr. T) — one of the four nucleotides that make up DNA; the others are adenine (A), cytosine (C), and guanine (G)

Timber — trade name for a computer algorithm used by AncestryDNA to reduce the effects of excess IBD (pile-ups) on DNA matching

time to most recent common ancestor (abbr. tMRCA or TMRCA) — an estimate of the number of years ago the most recent common ancestor of two or more people lived; usually based on an estimated mutation rate and average age of reproduction

TMRCA (also tMRCA) — abbreviation for time to most recent common ancestor

transition — a point mutation between two nucleotides that belong to the same chemical class, i.e., between A and G (both purines) or between C and T (both pyrimidines); see also transversion

transversion — a point mutation between two nucleotides that belong to different chemical classes, i.e., between a purine (A or G) and a pyrimidine (C or T); see also transition

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

triangulation group (abbr. TG) — a group of three or more people who all share the same segment of DNA

trio phasing — a method of phasing autosomal DNA results using data from a child and both parents

U


unsearchable tree — a fully private tree at Ancestry.com; no information from the tree will appear to other Ancestry users without the owner’s permission

upload — a DNA file generated by one testing company and copied to another database; can be a noun for the file itself or a verb for the activity of copying the file

upstream — the portion of a haplogroup tree ancestral to the node where a given SNP first appears

V


Verogen — a forensics equipment manufacturer that purchased GEDmatch in December 2019

visual phasing (abbr. VP) — a technique to assign DNA segments to the grandparent of origin using DNA matches for two or (ideally) more siblings

VP — abbreviation for visual phasing

W


WATO — abbreviation for the What Are the Odds? tool

WGS — abbreviation for whole genome sequencing

What Are the Odds? — a tool that uses shared autosomal DNA amounts to evaluate where one best fits into a family tree of tested relatives; especially useful for unknown parentage cases; part of the DNA Painter suite of tools

white paper — a report, usually produced by one of the DNA testing companies, describing the scientific details of a feature or service

X


X chromosome — a sex-determining chromosome present in all individuals; normally, women have two copies of the X chromosome and men have one copy of the X chromosome and one of the Y chromosome

Y


Y chromosome — a sex-determining chromosome normally present only in men

yDNA — DNA on the Y chromosome

Z


Still To Be Defined

Evil Twin

genome-wide association study (abbr. GWAS) —

Gephi

heteroplasmy

heterozygosity

homologous

homozygosity

imputation

institutional review board (abbr. IRB) —

IRB — abbreviation for institutional review board

Lazarus

linkage disequilibrium

most distant known ancestor (abbr. MDKA) —

microarray

next-generation sequencing (abbr. NGS or next-gen) —

next-gen — abbreviation for next-generation sequencing

phenome-wide association study (abbr. PWAS) —

polymorphism

population

reference panel

reference population

RootsFinder

Sorenson Molecular Genealogy Foundation (abbr. SMGF) —

whole genome sequencing (abbr. WGS) —

 

 

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