The DNA, genealogy, and GDAT terms used throughout this help. Terms link here from the pages that use them.
A profile (or kit) is a tested person whose DNA you're analyzing in GDAT. The active profile, chosen in the top-bar selector, scopes every screen. Managed in Profiles.
A match (or relative) is someone who shares DNA with your kit, as reported by a testing company. Your matches live in Matches.
A centimorgan (cM) measures the amount of DNA two people share — more shared cM generally means a closer relationship. GDAT uses total shared cM to suggest a relationship and to filter out distant matches on import.
A segment is a continuous stretch of shared DNA on one chromosome, defined by a start and end position (in Mbp) and measured in cM. Segments are what the Chromosome Browser paints. Ancestry doesn't publish segment data, so Ancestry-only kits have none.
Humans have 22 numbered chromosome pairs plus the sex chromosomes (X/Y). GDAT maps shared segments across chromosomes 1–22 and X.
A Single Nucleotide Polymorphism is a single-letter variation in DNA. Segment strength is partly judged by how many SNPs it spans; GDAT can exclude segments with too few SNPs as unreliable.
Two matches are in common with each other when both share DNA with your kit — though not necessarily on the same segment. ICW data drives clustering and triangulation. See the Person ICW tab and Analysis.
Triangulation is when your kit and two or more matches all share DNA on the same segment and are all ICW with each other — strong evidence they share a common ancestor on that segment. See Analysis → Triangulation.
A clustering technique that arranges your matches into a grid so that in-common-with groups — often your grandparent lines — separate visually. GDAT implements it as ICW Clusters. Background: Collins-Leeds method.
A tunable clustering method built on a correlation matrix of shared cM, with an ancestor overlay. See Analysis → Warthen Clusters and the WIC explainer.
Chromosome-aware clustering: it groups matches per chromosome by the segments they share in the same region. See Analysis → CMA and the CMA explainer.
An ahnentafel is an ancestor list numbered by the Sosa system: the person is 1, father 2, mother 3, and each person n has father 2n and mother 2n+1. Even numbers are men, odd are women. Shown in Ancestors and the Person Ahnentafel tab.
The most recent common ancestor shared between your kit and a match — the person (or couple) the shared DNA descends from. Record it on the Person MRCA tab or in Research.
A set of matches tied to a shared ancestral couple. GDAT builds family groups when you recompute family groups; they power the MRCA, Segment, and Group Compare analyses.
Which side of your family a match is on: P (paternal), M (maternal), B (both), or ? (unknown). Set it on the Person Overview tab.
Chromosome regions — centromeres and “pile-up” areas — where many unrelated people appear to share DNA, producing spurious matches. GDAT excludes your kit's false-positive regions from segment and triangulation views. Managed in Settings.
Colors you assign to family groups so you can track them across the MRCA and Segment screens. Click a group's swatch to recolor it.
The vendors GDAT imports from: Ancestry, 23andMe, FTDNA, MyHeritage, and GEDmatch. Each match is colored by its source throughout the app. Note that Ancestry provides no segment data.
GDAT 4 (Genealogical DNA Analysis Tool) is a DNAGedcom tool. © DNAGedcom LLC 2020–2026. Genealogical DNA Analysis Tool is provided as is with no guarantee given as to its performance.