DNA GENEALOGY GLOSSARY
Not everyone is familiar with genealogical terms, particularly when it comes to DNA. Included below are a few terms to give you a quick reference list. If you find something you would like added to the list, let me know.
Admixture estimates
Estimates the percentages of individuals’ early ancestors who came from specific geographical areas (see also biogeographical ancestry).
Autosomal DNA (atDNA)
DNA contained in the 22 non-sex chromosomes
Base
See nucleotide base.
Biogeographical ancestry
Estimates the percentages of individuals’ early ancestors who came from specific geographical areas (see also admixture).
Chromosome
A structure consisting of nucleotide bases and proteins. Humans have 46 of these arranged as 23 pairs, contained in the nucleus of each cell. Each pair contains one set from your father and one from your mother.
DNA
Deoxyribonucleic acid, a molecule carrying all the genetic instructions which govern all living organisms.
Ethnicity estimate
See Admixture estimate.
Fully identical region (FIR)
A segment of DNA that is shared on both copies of a chromosome (those received from both the father and the mother – normally only full siblings or double first cousins will have these).
Genetic genealogy
The application of DNA testing to genealogical research.
Half identical region (HIR)
A segment of DNA that is shared on just one of the two copies of a chromosome (matches either your father’s side or your mother’s side, not both).
Identical by chance (IBC)
A segment of DNA that matches between two people not because of a single ancestor, but because both sets of chromosomes are being read together as a single segment.
Identical by descent (IBD)
A segment of DNA that matches between two people because you are both related to a single ancestor.
Identical by population (IBP)
A segment of DNA that matches between two people because it is common to a group of people from the same area.
Identical by state (IBS)
A segment of DNA that matches between two people that is either IBC or IBP.
In common with (ICW)
Test-takers who share the same segment of DNA with both an initial test-taker and another match, but not necessarily with each other.
Mis-attributed parental event (MPE)
The individual recognized as the parent is not the biological parent. Also MAP (mis-attributed paternity) and NPE (not the parent expected).
Mitochondrial DNA (mtDNA)
A type of DNA found in the mitochondria of a cell inherited from all children from their mothers. Only passed on by daughters.
Most common recent ancestor (MCRA)
The most recent ancestor from whom DNA is inherited that is shared by two test-takers in a particular line of descent. If you are siblings, it would be your parents, if you are cousins, it would be your grandparents.
Nucleotide base
DNA has four nucleotide bases, adenine, cytosine, guanine and thymine, which always pair up in the same way, A with T and C with G. Each of these base pairs form a rung on the ladder found in DNA’s double helix structure.
Pedigree collapse
This occurs when marriages take place between cousins which reduces the number of ancestors.
Phasing
The process of identifying which sections of atDNA are inherited from which parent.
Triangulation
Test-takers who share the same segment of DNA with both an initial test-taker and another match, and all share exactly the same segment on the same chromosome within the pair.
Visual phasing
The process of identifying which sections of atDNA are inherited from which grandparent (is best using three siblings).
X-chromosome DNA (X-DNA)
DNA found in the X-chromosome. One of the sex chromosomes: females receive two X-DNA, one from their mother and one from their father; males receive one X-DNA from their mother.
Y-chromosome DNA (Y-DNA)
DNA found in the Y-chromosome. One of the sex chromosomes: males receive one Y-DNA from their father; females do not receive a Y-DNA