A Comprehensive Guide for Global Genealogists

By Genetic Voyage August 11, 2025

Analyzing DNA matches unlocks the secrets of your ancestry, connecting you to relatives across the globe, from New York to London to Stockholm. This 5000-word guide offers a step-by-step approach to understanding DNA matches, using tools like DNA Painter, GEDmatch, and techniques such as the Leeds Method and triangulation. Designed for beginners and advanced genealogists in the US, Europe, and beyond, this guide includes practical examples, visual suggestions, and actionable strategies to build your family tree. Whether you’re tracing an Ellis Island immigrant or solving a European “unknown parent” case, this guide will help you succeed. [Affiliate Disclosure: I may earn a commission from links at no cost to you. See our Privacy Policy.]

Introduction to DNA Matches

DNA matches are individuals who share segments of your genetic code, indicating a shared ancestor. The three main types of DNA tests for matching are:

1. Autosomal DNA: Tests all 22 non-sex chromosomes, ideal for finding cousins up to the 5th degree, widely used in the US and Europe.

2. Y-DNA: Traces paternal lines (males only), perfect for surname studies in American and European contexts.

3. mtDNA: Traces maternal lines (all genders), useful for deep ancestry across global migrations.

This guide explains how to analyze matches from AncestryDNA, MyHeritage, FamilyTreeDNA, Living DNA, and 23andMe, with examples tailored for american and European genealogists.

1. Understanding Autosomal DNA Matches

Autosomal DNA tests are the gold standard for genealogy, identifying cousins across all ancestral lines by measuring shared DNA in centimorgans (cM).

How Autosomal Matches Work

• Centimorgans (cM): A measure of shared DNA. Higher cM values indicate closer relationships:

  • 500+ cM: 1st–2nd cousins (shared grandparents or great-grandparents).

  • 50–200 cM: 3rd–5th cousins, ideal for tracing recent ancestors.

  • <20 cM: Distant cousins, useful with triangulation.

• Platforms: AncestryDNA excels for US matches, MyHeritage for European connections, and GEDmatch for global analysis.

• Shared Matches: If you and Match A share Match B, you likely share an ancestor on the same branch, a key feature on AncestryDNA and MyHeritage.

Practical Example: Tracing an Italian-American Ancestor

An American researcher tested with AncestryDNA, finding a 150 cM match with a tree listing Italian ancestors who immigrated to New York via Ellis Island in 1905. Shared matches formed a cluster of five cousins (50–100 cM), and GEDmatch’s One-to-One Comparison confirmed a 12 cM segment on chromosome 5. Using FamilySearch, the researcher found a 1905 passenger list and a New York marriage record, linking the match to a Calabrian family. Contacting the match revealed family lore about a 1920s Brooklyn grocer, confirming the connection.

Expert Techniques for Autosomal Matches

• Shared cM Tool: Use DNA Painter’s Shared cM Tool to estimate relationships. For example, 150 cM suggests a 3rd cousin (80% probability) or half-2nd cousin (15% probability).

• Leeds Method: Group matches into maternal and paternal clusters based on shared matches, ideal for separating lines in complex cases like unknown parentage.

• Triangulation: Confirm shared segments using GEDmatch’s chromosome browser. For example, a 10 cM segment shared by three matches on chromosome 12 indicates a common ancestor.

• What Are The Odds (WATO): Use DNA Painter’s WATO tool to build hypothetical trees and score relationship likelihoods.

• DNAGedcom Client: Download match data from AncestryDNA for spreadsheet analysis, sorting by cM, surnames, or locations like “New York” or “Calabria.”

Action Steps

1. Test with AncestryDNA for a robust US match database.

2. Upload raw DNA to GEDmatch and MyHeritage for European matches.

3. Prioritize matches with 50–200 cM for genealogical relevance.

4. Map segments with DNA Painter and use WATO for relationship hypotheses.

5. Contact matches to share trees and verify connections.

Learn how to interpret your results in our How to Interpret DNA Test Results guide.

2. Exploring Y-DNA Matches

Y-DNA tests trace paternal lines through the Y-chromosome (males only), ideal for surname studies and deep ancestry in American and European contexts.

How Y-DNA Matches Work

• Mechanism: Compares short tandem repeats (STRs) and single nucleotide polymorphisms (SNPs) to identify paternal-line matches. Matches share a haplogroup (e.g., R1b-M269, common in Western Europe) and similar STR markers.

• Genetic Distance: A genetic distance of 0–2 at 67 markers suggests a common ancestor within 200–400 years.

• Testing: FamilyTreeDNA offers Y-DNA tests (37, 67, or Big Y), popular among US and European genealogists.

Practical Example: Uncovering a British Paternal Line

A US researcher with a suspected British ancestor took a Y-DNA 67-marker test on FamilyTreeDNA, revealing haplogroup R1b-M269 and matches in Yorkshire, England, with a genetic distance of 1. The matches’ trees pointed to a Smith family from the 1700s. Joining the R1b-M269 haplogroup project connected them to a UK cousin whose ancestor was a 1750-born merchant who emigrated to Virginia. The National Archives provided 18th-century parish records confirming the Smith lineage, linking the US and UK branches.

Expert Techniques for Y-DNA

• Big Y Testing: Identifies specific SNPs (e.g., R1b-M269>L21) for precise lineage tracing within 100–200 years.

• Haplogroup Projects: Join FamilyTreeDNA projects to collaborate with matches and access group analyses.

• Surname Projects: Connect with matches sharing surnames like “Smith” to solve brick walls.

• Phylogeography: Use ISOGG to study haplogroup migrations, such as Anglo-Saxon or Viking movements to Britain.

Action Steps

1. Take a Y-DNA 37-marker test with FamilyTreeDNA.

2. Join haplogroup and surname projects on FamilyTreeDNA.

3. Upgrade to Big Y for detailed SNP analysis.

4. Cross-reference matches with The National Archives or FamilySearch.

Explore Y-DNA haplogroups at ISOGG.

3. Analyzing mtDNA Matches

mtDNA tests trace maternal lines through mitochondrial DNA, available to all genders, but best for deep ancestry due to slow mutation rates.

How mtDNA Matches Work

• Mechanism: Compares mitochondrial mutations to identify matches with shared maternal ancestry, often sharing a haplogroup (e.g., H, common in Europe).

• Limitations: Slow mutation rates make mtDNA less useful for recent genealogy (within 500 years).

• Testing: FamilyTreeDNA offers mtDNA tests (HVR1, HVR2, or full sequence).

Practical Example: Tracing a German Maternal Line

A European researcher took an mtDNA full-sequence test on FamilyTreeDNA, revealing haplogroup H1, common in Germany. Matches included a US cousin with a Bavarian ancestor from the 1800s. FamilySearch provided an 1850 German parish record confirming the maternal line. Due to mtDNA’s limitations, the researcher used AncestryDNA to find a 100 cM autosomal match, strengthening the connection to a Bavarian family that emigrated to Ohio.

Expert Techniques for mtDNA

• Full Sequence Testing: Opt for full mtDNA sequencing for higher resolution.

• Haplogroup Projects: Join FamilyTreeDNA mtDNA projects to connect with matches.

• Combine with Autosomal: Use mtDNA for deep ancestry and autosomal DNA for recent connections.

• Migration Studies: Research maternal-line migrations (e.g., German to US) via FamilySearch.

Action Steps

1. Take an mtDNA full-sequence test with FamilyTreeDNA.

2. Join mtDNA haplogroup projects.

3. Use autosomal matches on AncestryDNA for recent genealogy.

4. Cross-reference with FamilySearch.

Learn how to combine DNA tests in our Finding an Unknown Father with DNA guide. (coming soon)

4. Using Shared Matches and Clustering

Shared matches and clustering tools organize your DNA matches into groups, revealing shared ancestral lines.

How Shared Matches and Clustering Work

• Shared Matches: If you and Match A share Match B, you likely share a common ancestor. Available as “in common with” on AncestryDNA or “shared matches” on MyHeritage.

• Clustering: Tools like MyHeritage’s AutoCluster or Genetic Affairs on GEDmatch create visual groups of matches with shared DNA.

Practical Example: Uncovering an Afro-American Cluster

A US researcher ran AutoCluster on MyHeritage, grouping eight matches (50–150 cM) with trees pointing to South Carolina. A 100 cM match shared a tree listing an 1880s ancestor. Triangulation on GEDmatch confirmed a 10 cM segment on chromosome 8. FamilySearch provided 1870 US Census records showing a freedmen’s community, and collaboration with the match revealed oral history about a post-Civil War migration, confirming the cluster’s origin.

Expert Techniques for Clustering

• AutoCluster Settings: Set cM thresholds (20–400 cM) on MyHeritage for relevant matches.

• Genetic Affairs AutoTree: Reconstructs match trees to identify common surnames or locations (e.g., “South Carolina”).

• Chromosome Browser: Verify segment overlaps with GEDmatch’s chromosome browser.

• Spreadsheet Analysis: Export cluster data using DNAGedcom to analyze surnames and locations.

Action Steps

1. Run AutoCluster on MyHeritage with a 20–400 cM threshold.

2. Verify segments with GEDmatch’s chromosome browser.

3. Build trees for cluster members on MyHeritage.

4. Contact matches to share information.

Explore clustering tools at Genetic Affairs.

5. Triangulation and Chromosome Mapping

Triangulation and chromosome mapping confirm shared ancestors by identifying overlapping DNA segments.

How Triangulation Works

• Mechanism: If you, Match A, and Match B share a segment on the same chromosome (e.g., 10 cM on chromosome 8), you likely inherited it from a common ancestor.

• Tools: GEDmatch’s One-to-One Comparison or FamilyTreeDNA’s chromosome browser verifies overlaps.

• Mapping: DNA Painter visualizes segments, assigning them to maternal or paternal lines.

Practical Example: Confirming a Scottish Ancestor

A European researcher triangulated a 12 cM segment on chromosome 8 shared by three Scottish matches, suggesting a common ancestor from the 1700s. DNA Painter mapped the segment, and The National Archives provided 1750 parish records confirming a Campbell family connection. The researcher’s US cousin, tested via AncestryDNA, shared the same segment, linking to a 19th-century Scottish immigrant.

Expert Techniques for Triangulation

• Segment Search: Use GEDmatch’s Segment Search to find additional matches sharing specific segments.

• Phased Data: Phase parental DNA on GEDmatch to separate maternal and paternal segments.

• WATO Integration: Combine triangulation with DNA Painter’s WATO tool to score relationship likelihoods.

• Minimum Segment Size: Focus on segments >10 cM, but consider smaller segments if triangulated across multiple matches.

Action Steps

1. Triangulate matches with GEDmatch’s One-to-One Comparison.

2. Map segments with DNA Painter.

3. Verify with records from The National Archives.

4. Use WATO for relationship hypotheses.

Explore family tree building in our 5 Tips for Building a Family Tree.

6. Combining DNA Matches with Historical Records

Pairing DNA matches with historical records provides context and confirmation for your findings.

Why Combine DNA and Records?

• Verification: Records confirm genetic relationships and prevent errors.

• Context: Historical events (e.g., US Civil War, European migrations) explain DNA patterns.

• Key Archives:

  • USA: FamilySearch for census and BMD records; Ellis Island for immigration.

  • UK: The National Archives for parish and census records.

  • Europe: Deutsche Digitale Bibliothek for Germany; Riksarkivet for Sweden.

Practical Example: Solving a Swedish “Fader Okänd” Case

A US researcher with Swedish roots found a 200 cM match on MyHeritage with a tree pointing to Östergötland. Riksarkivet revealed a 1909 “fader okänd” birth record from a market day, suggesting a transient father. Barnavårdsnämnden records noted a possible Andersson surname, matching the match’s tree. Triangulation on GEDmatch confirmed a 15 cM segment, and collaboration with the match revealed a traveling merchant ancestor.

Expert Techniques

• US Census Records: Use FamilySearch to trace US ancestors, especially post-1850 censuses.

• European Parish Records: Access The National Archives or Riksarkivet for detailed BMD records.

• GEDCOM Integration: Import records into MyHeritage trees.

• Migration Analysis: Study Ellis Island for US immigration patterns.

Action Steps

1. Search FamilySearch for US and global records.

2. Access Riksarkivet for Swedish records.

3. Import records into MyHeritage.

4. Check barnavårdsnämnden records for illegitimacy cases.

Access global records at FamilySearch.

7. Advanced Tools for DNA Match Analysis

Advanced tools streamline and enhance your DNA match analysis.

Key Tools

• DNA Painter: Maps shared segments to chromosomes, visualizing ancestral contributions (e.g., a 100 cM segment on chromosome 5).

• GEDmatch One-to-One Comparison: Verifies segment overlaps for triangulation.

• What Are The Odds (WATO): Tests relationship hypotheses with hypothetical trees.

• DNAGedcom Client: Downloads match data for spreadsheet analysis.

• Genetic Affairs AutoCluster: Groups matches visually, highlighting shared ancestry.

Practical Example: Mapping a Polish Connection

A European researcher used DNA Painter to map a 100 cM segment shared with a Polish match, confirming a Krakow ancestor. AutoCluster on MyHeritage grouped six related matches, and GEDmatch’s Segment Search identified additional cousins. FamilySearch provided 1880 Polish parish records, confirming a migration to the US.

Action Steps

1. Create a DNA Painter profile to map segments.

2. Use GEDmatch’s One-to-One Comparison.

3. Run AutoCluster on MyHeritage.

4. Download match data with DNAGedcom.

 Discover clustering in our How DNA Matching Works guide. (coming soon)

8. Common Pitfalls to Avoid

Avoid these mistakes for accurate DNA match analysis:

• Over-Relying on Predicted Relationships: A 150 cM match may be a 3rd cousin or half-2nd cousin. Verify with DNA Painter’s Shared cM Tool.

• Ignoring Distant Matches: Matches with 10–20 cM can reveal ancestors if triangulated on GEDmatch.

• Neglecting Records: Cross-reference with FamilySearch or The National Archives.

• Not Testing Relatives: Test parents or siblings with AncestryDNA for clearer matches.

• Failing to Contact Matches: Use MyHeritage messaging to collaborate.

• Not Updating Results: Check AncestryDNA monthly for new matches.

9. Action Plan for Analyzing DNA Matches

1. Test with AncestryDNA and MyHeritage.

2. Take a Y-DNA or mtDNA test with FamilyTreeDNA.

3. Upload to GEDmatch for global matches.

4. Map segments with DNA Painter and use WATO.

5. Run AutoCluster on MyHeritage.

6. Research records on FamilySearch and The National Archives.

7. Contact matches and join Genealogy DNA on Facebook.

Avoid errors with our 5 Mistakes to Avoid in DNA Testing.

10. Case Study: A Transatlantic Breakthrough

A US researcher tested with AncestryDNA, finding a 200 cM match with a tree listing Irish ancestors in Boston. AutoCluster on MyHeritage grouped eight matches, including a UK cluster from Yorkshire. Triangulation on GEDmatch confirmed a 15 cM segment on chromosome 5. Ellis Island records showed a 1905 Irish immigrant, and The National Archives confirmed a Yorkshire ancestor from 1750. A Y-DNA test revealed haplogroup R1b-L21, linking to Irish matches. Collaboration via Genealogy DNA on Facebook expanded the tree to the 1600s.

Conclusion

Analyzing DNA matches bridges your past across continents. Start with AncestryDNA and explore 700 Global Genealogy Resources. Contact geneticvoyage@hotmail.com for support.

Related Guides:
How DNA Matching Works | Finding an Unknown Father with DNA | Beginner’s Guide to Genealogy Research

Affiliate Disclosure: I may earn a commission from links at no cost to you. See our Privacy Policy.