How DNA Matching Works
How DNA Matching Works: A Beginner's Guide to Genetic Genealogy
Understand shared DNA, centimorgans, segments and shared matches, and turn a list of matches into real genealogy clues.
How DNA matching works is one of the most important concepts to understand when using DNA for genealogy. A DNA match is another person whose DNA contains enough shared genetic material with yours to suggest that you may share a common ancestor.
DNA matching can help you find relatives, investigate unknown branches of your family tree, test traditional genealogy research, and generate new clues when historical records reach a dead end.
But a DNA match is not automatically proof of a specific relationship. To understand what a match means, you need to look at the amount of shared DNA, the number and size of shared segments, family trees, surnames, locations, and other evidence.
💡 Quick Fact: A DNA Match Is a Clue, Not a Complete Family Tree
DNA matching can indicate that two people are related, but the match alone usually does not tell you exactly how they are related. The strongest genealogy research combines DNA evidence with family trees and historical records, a principle reflected in the Genetic Genealogy Standards published by the Board for Certification of Genealogists.
How DNA Matching Works: Quick Overview
At a basic level, DNA matching works by comparing parts of your DNA with the DNA of other people who have tested with the same service or whose data has been made available through that service.
When enough DNA appears to be shared, the testing company identifies the person as a potential DNA match and estimates a possible relationship.
From DNA Test to Genealogy Research
The seven steps every DNA matching service follows, ending with your own research.
- You take an autosomal DNA test or use eligible DNA data.
- The testing service analyzes your DNA.
- Your DNA is compared with other participants.
- Shared DNA segments are identified.
- The amount of shared DNA is measured, commonly in centimorgans (cM).
- The service estimates possible relationships.
- You investigate the match using genealogy evidence.
The exact algorithms, thresholds, databases, and features vary between companies, so the same person may not appear as a match on every DNA testing platform. MyHeritage, for example, notes that matching algorithms and thresholds can vary between providers.
Why DNA Matching Matters for Genealogy
Traditional genealogy relies heavily on records such as birth certificates, census records, church registers, marriage records, immigration documents, and other historical sources.
DNA can provide another type of evidence. Suppose your family tree suggests that two branches connect through a particular ancestor. A DNA match with a person who descends from that same family line can provide supporting evidence.
DNA can also help when records are missing, contradictory, difficult to locate, or unavailable because of an adoption, name change, migration, or other circumstance.
What DNA Matching Can Help You Do
- Find biological relatives: Discover people who may belong to branches of your family.
- Test genealogy theories: Look for DNA evidence that supports a proposed relationship.
- Identify unknown family branches: Use clusters of matches to investigate an unfamiliar surname or location.
- Break through brick walls: Generate new research leads when traditional records stop.
- Investigate unknown parentage: DNA matches can sometimes provide important clues about biological family connections.
🌳 Genealogy Principle
The most useful DNA research does not replace traditional genealogy. Instead, DNA evidence and historical records can be used together to build a stronger case for a family relationship. The ISOGG Wiki defines genetic genealogy as the use of DNA testing in combination with traditional genealogical and historical records.
How DNA Matching Works Step by Step
Step 1: You Take a DNA Test
Most consumer genealogy matching begins with an autosomal DNA test. Autosomal DNA comes from both sides of your family, making it useful for finding relatives across many branches of your family tree.
For example, a person can potentially match relatives connected through their mother's family as well as relatives connected through their father's family.
If you are new to DNA testing, start with our guide to getting started with DNA testing for genealogy.
Step 2: Your DNA Is Analyzed
The testing company analyzes selected genetic markers from your sample. Consumer DNA testing commonly examines large numbers of genetic positions called SNPs (single nucleotide polymorphisms). The company then uses this information for features such as DNA matching and ancestry analysis. According to the NHGRI Talking Glossary of Genomic and Genetic Terms, SNPs are the most common type of genetic variation among people.
Step 3: Your DNA Is Compared With Other Testers
The service compares your genetic data with the data of other people in its matching database who are eligible to participate in DNA matching.
Ancestry explains that its DNA Matches are generated by comparing your DNA with other people who have opted into matching and are likely to be related based on the comparison. Other providers use their own databases, algorithms, and matching thresholds.
Step 4: Shared DNA Segments Are Identified
When two people have matching stretches of DNA, those sections can be identified as shared DNA segments. These segments may have been inherited from a common ancestor. The ISOGG Wiki describes identical by descent (IBD) segments as matching segments inherited from a recent common ancestor without intervening recombination.
MyHeritage describes shared DNA segments as sections of DNA that are identical between two individuals and notes that they were most likely inherited from a common ancestor.
What Shared DNA Segments Look Like
Matching stretches of DNA appear as highlighted segments along the same chromosome.
Illustrative example only. Three numbers describe a match: total cM, number of segments, and largest segment.
Step 5: Shared DNA Is Measured
The amount of shared DNA is commonly expressed in centimorgans (cM). In general, close relatives share more DNA than distant relatives. However, there is considerable variation in the amount of DNA inherited from different ancestors, so cM should be treated as evidence for a range of possible relationships rather than an exact answer. The National Human Genome Research Institute (NHGRI) defines a centimorgan as a unit of measure for the frequency of genetic recombination.
📏 What Is a Centimorgan?
A centimorgan, abbreviated cM, is a unit used in genetic genealogy to describe genetic distance. DNA matching services use shared cM to help estimate how closely two people may be related. According to the ISOGG Wiki, one centimorgan corresponds to about 1 million base pairs in humans on average and is equal to a 1% chance that a marker at one genetic locus will be separated from a marker at a second locus due to crossing over in a single generation.
Understanding Centimorgans (cM)
If you are learning how DNA matching works, centimorgans are one of the first concepts you should understand.
A match might share a relatively large amount of DNA with you or a much smaller amount. In general, larger amounts of shared DNA are associated with closer relationships, while smaller amounts can indicate more distant relationships. However, the same amount of shared DNA can sometimes be consistent with several different relationships.
For example, a particular cM total should not automatically be interpreted as proof that someone is your third cousin, fourth cousin, or another exact relationship. Instead, use the cM value to create a range of possible relationships and then investigate the genealogy evidence.
The Shared cM Project, a collaborative research project led by Blaine Bettinger, provides observed ranges of shared DNA for nearly 50 different genealogical relationships, based on tens of thousands of submissions from genealogists. The DNA Painter Shared cM Tool makes this data accessible as an interactive visualization. MyHeritage also provides example average ranges for relationships such as parents, siblings, grandparents, aunts/uncles, and first cousins, while emphasizing that actual shared DNA values can be higher or lower.
Three Numbers to Pay Attention To
Depending on the DNA testing company, you may see several measurements associated with a match.
| Measurement | What it tells you |
|---|---|
| Total shared DNA | The total amount of DNA shared with the match. |
| Number of shared segments | How many separate DNA segments you share. |
| Largest shared segment | The size of the largest individual shared segment. |
MyHeritage specifically uses shared DNA, shared segments, and the largest segment as parameters for evaluating DNA matches.
⚠️ Important
Do not identify a relationship from total cM alone. Two people who share a similar amount of DNA can sometimes fit more than one genealogical relationship. The ISOGG Wiki notes that known second cousins on average share around 212 cM, but in extreme cases can share as little as 47 cM or as much as 760 cM, illustrating why ranges matter more than single values.
How DNA Companies Predict Relationships
DNA testing companies use the amount and pattern of shared DNA to estimate a possible relationship. You might therefore see descriptions such as:
- Parent or child
- Sibling or close family
- Aunt, uncle, niece, or nephew
- Cousin relationships
- Distant relative
The exact labels and relationship ranges vary between providers. A predicted relationship should therefore be treated as a starting point for research rather than a guaranteed identification.
Why Relationship Predictions Can Be Ambiguous
DNA inheritance is random because recombination shuffles genetic material during the formation of egg and sperm cells. According to the ISOGG Wiki, recombination is the exchange of DNA segments between the two copies of a chromosome, and each chromosome is cut at one or two random spots. You do not inherit exactly the same amount of DNA from every ancestor at the same generational distance. This means that two relatives with the same genealogical relationship can share different amounts of DNA. Research published in the journal Genetics further demonstrates that recombination patterns vary across the genome and between individuals, contributing to this uncertainty [Identity by descent: variation in meiosis, across genomes, and in populations].
As relationships become more distant, there can also be more uncertainty about whether a small shared segment represents a genealogically meaningful connection.
Are Small DNA Matches Useful?
Small DNA matches can sometimes be useful, but they require more careful analysis than stronger matches. A small match may represent a genuine distant relationship, but small segments can also be less informative and may sometimes result from shared DNA that does not come from a recent common ancestor.
MyHeritage specifically warns that very small matches can sometimes represent identity by state (IBS) rather than identity by descent (IBD), particularly among more distant matches. The ISOGG Wiki defines identity by state as alleles that are the same irrespective of whether they are inherited from a recent ancestor, whereas identity by descent refers to segments inherited from a common ancestor without intervening recombination.
This is why a small match should normally be considered together with other evidence such as shared surnames, locations, family trees, and additional shared matches.
🔎 Research Tip
Do not automatically delete every distant match. Instead, prioritize matches that also provide useful genealogy clues such as a family tree, shared surnames, shared locations, or multiple relatives connecting to the same family branch.
What Are Shared DNA Matches?
One of the most useful features for genealogy is the ability to identify people who match both you and another DNA match. These are often called shared matches. Shared matches can help you determine which side of your family a DNA match may belong to. MyHeritage describes shared DNA Matches as people who are genetically related to both you and your DNA match, and notes that they can help identify which side of the family a match may be connected to.
How Shared Matches Reveal a Family Side
A new match who also matches a known maternal cousin probably belongs to the maternal side.
A shared-match pattern is a clue, not proof of the exact relationship.
For example, imagine that you have a known maternal cousin who appears as a match with another person. If that other person also shares DNA with your known maternal cousin, the shared-match pattern can provide a clue that the new match may belong to your maternal side. It does not prove the exact relationship, but it can help narrow your research.
MyHeritage describes shared DNA matches as people who are genetically related to both you and your DNA match, and notes that they can help identify which side of the family a match may be connected to. The feature shows matches that are the closest, on both the paternal and the maternal side, with the closest estimated relationships at the top of the list.
Why Family Trees Matter When Analyzing DNA Matches
DNA tells you that two people may be related. A family tree can help explain how. When reviewing a DNA match, look for:
- Shared surnames
- Shared ancestral locations
- Common ancestors
- Overlapping family-tree branches
- Shared matches
- Migration patterns
- Historical records supporting the proposed connection
A DNA match with a detailed public family tree can therefore be much easier to investigate than a match with no genealogical information. This is one reason why building your own family tree before or after taking a DNA test can make your DNA results much more useful.
Our beginner's guide to genealogy research can help if you are also learning traditional family-history research.
DNA Matching Tools You Can Use
Once you understand the basics of how DNA matching works, specialized tools can help you analyze your matches more effectively.
DNA Testing Company Match Tools
Major genealogy DNA services provide their own matching systems. Depending on the provider, you may be able to examine shared DNA, predicted relationships, family trees, shared matches, and other information.
1. MyHeritage DNA Matching
MyHeritage combines DNA matching with family-tree information and other genealogy features. Its DNA Match pages can provide information such as shared DNA, shared segments, largest segments, possible relationships, shared surnames, shared matches, and pedigree information. MyHeritage also provides a Chromosome Browser that displays half-identical regions and allows you to compare up to seven matches at a time.
MyHeritage also allows DNA matching for eligible DNA data uploaded from certain other services, according to its current help documentation.
🧭 MyHeritage Research Tip
If you use MyHeritage for DNA genealogy, look beyond the predicted relationship. Family trees, shared surnames, shared matches, and geographic information can provide additional clues for identifying a common ancestor.
2. AncestryDNA
AncestryDNA provides DNA Matches based on comparisons between people who have tested and participate in DNA matching. Its DNA matching system includes predicted relationship categories and shared DNA information. Ancestry's AncestryDNA Matching White Paper describes the process by which they identify identical-by-descent segments and estimate relationships. Ancestry also provides additional genealogy resources that can be used alongside DNA research.
3. FamilyTreeDNA
FamilyTreeDNA is particularly relevant to researchers interested in genetic genealogy, including autosomal DNA as well as specialized Y-DNA and mtDNA testing. The ISOGG Wiki explains that Y-DNA testing involves short tandem repeat (STR) and, sometimes, SNP testing of the Y-chromosome, while mtDNA traces a person's matrilineal ancestry. For beginners, autosomal DNA is generally the most relevant starting point for finding relatives across multiple branches of a family tree.
4. GEDmatch
GEDmatch is a separate genealogy DNA platform that can be used for additional DNA analysis. Features and access levels can change, so check the current platform information before relying on a particular tool.
What Is a Chromosome Browser?
A chromosome browser is a tool that can show where shared DNA segments occur along chromosomes. The ISOGG Wiki describes it as a tool that allows comparison between one or more matches to see which segments of DNA are shared in common and their locations. This can be particularly useful when you move beyond basic match lists and begin investigating whether multiple people share the same segment.
MyHeritage describes its Chromosome Browser as a visual tool for locating shared DNA segments between people. For a practical introduction, try our free DNA Chromosome Browser. You can also continue to our more advanced guide to DNA triangulation.
What Is DNA Triangulation?
DNA triangulation is an advanced technique in which you investigate whether you and multiple DNA matches share the same DNA segment with one another. The ISOGG Wiki explains that in autosomal DNA testing, triangulation is the term used to describe the process of reviewing the pedigree charts of people who match on the same IBD autosomal DNA segment to see if a common ancestor can be found.
Triangulation: One Segment, Three People
If three or more people share the same relevant segment, and the genealogy evidence points toward the same family branch, this can provide a stronger research clue about a possible common ancestor.
Triangulation is more advanced than simply looking at your list of DNA matches, so beginners should first become comfortable with shared DNA, cM, family trees, and shared matches. When you are ready, read our advanced DNA triangulation guide.
Four Levels of Evidence: What Each One Can and Cannot Show
When people say "the DNA proves we are related," they are often mixing together four very different kinds of information. Each answers a different question, and each has limits. Keeping them separate is one of the most effective ways to avoid treating a predicted relationship as a settled conclusion.
| Level of evidence | What it can show | What it cannot show |
|---|---|---|
| 1. Total shared DNA (cM) | That you and the match are probably genetically related, and roughly how closely, expressed as a range of candidate relationships. | The exact relationship, the common ancestor, which side of your family the match belongs to, whether the relationship is full or half, or which of the two of you is in the older generation. |
| 2. Shared matches | Which side or branch of your tree the match probably belongs to, because people who match both of you tend to descend from the same ancestral couple. | The exact relationship or the specific ancestor. Two people can also be linked through more than one line, and a cluster only reflects who has tested, so a missing shared match proves nothing. |
| 3. Overlapping DNA segments | That several people may have inherited the same stretch of DNA from one ancestral source. This is stronger than simply being on each other's match lists, and is the basis of triangulation. | Who that ancestor is. Small segments can be identical by state rather than by descent, and an overlap is only meaningful when it is checked against the people's trees. |
| 4. Genealogically verified common ancestor | A documented line of descent from a named ancestor or couple to each person, supported by records such as birth, marriage and census entries. | That the DNA you share really came from that ancestor, especially several generations back, and whether the biological parentage matches the recorded parentage in every generation. Records name registered parents, which is usually, but not always, the biological story. |
🧱 Why the Order Matters
The four levels build on each other: cM gives a range, shared matches pick a branch, overlapping segments support a single ancestral source, and records name the ancestor. A strong conclusion is one where all four levels agree. When they disagree, that is not a failure; it is a signal to look for a half relationship, a second family connection, a misattributed parent or a tree error.
Worked Example: One 350 cM Match, From First Look to Documented Conclusion
The following case is fictional. The names, dates and parish are invented, but the cM figures are taken from the published Shared cM Project (version 4), so you can follow the same reasoning with your own matches.
The starting point
Anna (born 1985) has taken a DNA test. A new match called Mats appears with 350 cM of shared DNA across 17 segments, with a largest segment of 48 cM. Mats was born in 1957. The service predicts "1st–2nd cousin" or a similar label. Anna wants to know how they are actually related.
Step 1: Turn 350 cM Into a List of Candidates
Instead of accepting the single label from the testing company, Anna checks which relationships have been observed to share about 350 cM.
| Relationship | Average cM | Observed range | Does 350 cM fit? |
|---|---|---|---|
| First cousin | 866 | 396–1,397 | Unlikely, as 350 is below the observed range |
| First cousin once removed (1C1R) | 433 | 102–980 | Yes, comfortably inside the range |
| Half first cousin | 449 | 156–979 | Yes |
| Half great-aunt/uncle (or half great-niece/nephew) | 431 | 184–668 | Yes |
| Second cousin | 229 | 41–592 | Yes, but above average |
| First cousin twice removed (1C2R) | 221 | 33–471 | Yes, but in the upper part of the range |
| Half first cousin once removed | 224 | 62–469 | Yes, but in the upper part of the range |
Averages and ranges are observed values from the Shared cM Project v4 (Bettinger, 2020), not guarantees, and they do not model endogamy or pedigree collapse. Use the DNA Painter Shared cM Tool to see the current probabilities for your own number.
After step 1, Anna has no single answer. At least six relationship types remain possible, and a seventh, a full first cousin, cannot be completely ruled out. The cM total has done its job: it narrowed the field and produced hypotheses, but it cannot choose between them.
Step 2: Decide What Extra Information Is Needed
To choose between the candidates, Anna needs information that the cM total does not contain:
- Generation gap: Mats was born 28 years before Anna. That favors relationships with a generation difference ("once removed", aunt/uncle types) over a same-generation cousin.
- Which side of the family: Shared matches should show whether Mats clusters with Anna's maternal or paternal relatives.
- Full or half relationship: Only the parentage of the people in between can settle this, and the DNA alone cannot.
- Mats's family tree, surnames and places: These suggest where to look for the connecting ancestors.
- Other testers in the family: If Anna's mother or a cousin has also tested, their results with Mats add another measurement.
- Warning signs: Endogamy or several known connections to the same family would make the cM range wider and the table above less reliable.
Step 3: Check Shared Matches and Overlapping Segments
Anna opens Mats's shared matches. Mats is also a match with Anna's mother Karin (about 690 cM, a value consistent with first cousins), with Anna's maternal uncle, and with a maternal second cousin. None of Anna's paternal relatives match Mats.
This points to the maternal side and fits one specific idea: if Mats is a first cousin of Karin, then Mats is a first cousin once removed of Anna. A chromosome browser also shows that Mats's largest segment (48 cM) overlaps with segments that Mats shares with Karin and with the maternal second cousin, which supports a single maternal-line source for that stretch of DNA.
What has not been shown yet: which ancestor is the link, and whether Mats is a full or half relative. The shared matches have supplied a side and the overlap has supplied supporting evidence, but neither has named a person.
Step 4: Compare the Trees
Mats's public tree lists his father as Gösta Andersson, born 1928 in a rural parish, but goes no further back. Anna's tree shows her maternal grandmother Elsa Andersson, born 1926 in the same parish, daughter of Johan and Hilda Andersson.
This gives a working hypothesis (H1): Gösta and Elsa were full siblings, children of Johan and Hilda. But there are traps:
- Andersson is an extremely common surname in Sweden, so the shared surname is a weak clue and the shared parish is only a moderate one.
- H2: Gösta and Elsa could have been half siblings with only one parent in common. That would make Mats a half first cousin once removed once, and a lower average cM would be expected, although 350 cM is still within the observed range.
- H3: The two Anderssons may be unrelated, and the DNA connection could run through a different line, such as a second-cousin relationship.
Step 5: Test the Hypothesis With Documents
At this point DNA has produced a hypothesis, not a result. Anna now turns to records to test it, and each record answers a specific question:
Records that would test H1, H2 and H3
- Elsa's birth or baptism record (1926): names her parents. If these are Johan and Hilda, Anna's tree is confirmed at this point.
- Gösta's birth or baptism record (1928): names his parents. If both Johan and Hilda are named, Gösta and Elsa were full siblings (H1). If a different mother is named, they were half siblings (H2).
- A census or household record (for example, 1930): if Elsa and Gösta appear as children in the same household with Johan and Hilda, this independently supports the sibling relationship and reduces the chance that the two Anderssons are unrelated (H3).
- Gösta's marriage record and Mats's birth record (1957): connect Mats to Gösta as his father.
- Karin's birth record (1960) and Elsa's marriage record: connect Anna's mother to Elsa.
Together, these records form a chain: Anna → Karin → Elsa → Johan and Hilda ← Gösta ← Mats.
Suppose all the records are found and they agree: both children are named with the same two parents, they appear together in the 1930 household, and the later records connect each to Mats and to Karin. The paper trail then shows that Mats is Anna's first cousin once removed, and the 350 cM falls comfortably within the observed range for that relationship, so the DNA and the documents agree.
How the Conclusion Changes as Evidence Is Added
Each new type of evidence narrows the hypothesis. Only the last one names a documented ancestor.
Bar length shows how well supported the working conclusion is. It is never full, because records show registered parentage rather than proof of biological descent.
What Would Have Changed the Conclusion
Gösta's birth record names a different mother
Gösta and Elsa would then be half siblings, and Mats would be a half first cousin once removed. The relationship label would change even though the DNA numbers stay the same.
No record connects the two Anderssons
Without a documented link, the DNA stays a hypothesis. Anna would keep the match on file and test other candidates, such as a second-cousin connection through another line.
Mats matches Anna's paternal relatives too
A match on both sides suggests more than one connection or a possible endogamy effect, so the cM table could be misleading.
The records conflict with each other
For example, two different birth years for Gösta. Anna would have to resolve or at least report the conflict before reaching a conclusion.
The Final, Cautious Conclusion
📝 Research note (fictional example)
Conclusion: Mats is very likely Anna's first cousin once removed, through Johan and Hilda Andersson, who were the parents of both Elsa (b. 1926) and Gösta (b. 1928).
Evidence: 350 cM across 17 segments, within the observed range for 1C1R; a generation gap of 28 years; shared matches only on Anna's maternal side, including her mother (about 690 cM); an overlapping segment on the maternal line; birth records of Elsa and Gösta naming the same parents; a household census entry listing both children; and records linking Gösta to Mats and Elsa to Anna's mother.
Limitations: The records show registered parentage, not confirmed biological parentage. Only one family line was tested. The cM statistics do not model endogamy. The conclusion is well supported but would be revised if new records or matches contradicted it.
Notice the wording: very likely, well supported, would be revised. A cautious conclusion states what the evidence supports, names its limits, and records its sources so that someone else can check it. The Board for Certification of Genealogists emphasizes the same habits through the Genealogical Proof Standard: reasonably exhaustive research, source citations, careful analysis, resolution of conflicting evidence, and a soundly reasoned written conclusion.
⚠️ This Example Is Deliberately Tidy
Real research is rarely this clean. Records may be missing, names may be spelled differently, and the DNA and documents may disagree.
When they disagree, do not discard whichever one is inconvenient. Record the conflict and investigate it.
Common DNA Matching Mistakes to Avoid
1. Assuming the Predicted Relationship Is Exact
A predicted relationship is an estimate. Treat it as a research hypothesis and investigate other possibilities.
2. Looking Only at Total cM
Total shared DNA is important, but the number and size of shared segments and the wider genealogy context can provide additional information.
3. Ignoring Family Trees
A DNA match without genealogical context can be difficult to identify. Family trees, surnames, locations, and records can transform a match into a useful research lead.
4. Treating Every Small Match as Proof
Small matches can be useful, but they need more supporting evidence. Very distant matches can be difficult to interpret confidently.
5. Ignoring Shared Matches
Shared matches can help you determine which branch of your family a new match may belong to.
6. Forgetting Traditional Genealogy
DNA should not be treated as a replacement for documentary research. Whenever possible, verify a proposed relationship using historical records.
✅ Best Practice
Think of DNA matching as a process of building evidence. Start with the genetic connection, then use family trees, shared matches, surnames, locations, and historical records to develop and test a genealogy hypothesis.
How to Analyze a DNA Match: Beginner Workflow
Once your DNA results are available, use a consistent process rather than opening matches randomly.
Step 1: Start with stronger matches
These are generally easier to interpret.
Step 2: Record the shared DNA
Note the total cM and other available measurements.
Step 3: Look at the family tree
Search for surnames, locations, and potential ancestors.
Step 4: Check shared matches
Determine whether the match connects to known relatives.
Step 5: Identify a possible family branch
Use the evidence to narrow down where the match belongs.
Step 6: Search historical records
Test the proposed connection against documentary evidence.
Step 7: Record your conclusion
Keep notes so you can return to the match later.
The 350 cM worked example above follows exactly these seven steps. For a much more advanced approach, see our guide to analyzing DNA matches, where we go deeper into DNA research strategies.
Use Our Free DNA Relationship Calculator
If you know how much DNA you share with a match, our DNA Relationship Probability Calculator can help you explore possible relationships. Remember that a calculator provides possibilities rather than a definitive identification. Use the result together with family-tree evidence and historical research.
🧮 Calculator Reminder
A DNA relationship calculator can help organize possibilities from shared DNA, but it cannot identify your common ancestor by itself.
DNA Matching and Privacy
DNA is highly personal information, so privacy should be part of your genealogy research strategy. Before testing or uploading DNA data, review the current privacy controls of the service you plan to use. Check how the service handles:
- DNA matching participation
- Research participation
- Sharing of DNA information
- DNA data deletion
- Account management
- Access to DNA matches
For example, MyHeritage currently provides DNA privacy settings that allow users to control participation in DNA Matching and certain shared-segment features. MyHeritage states that it will not sell or license genetic data without explicit consent and prohibits law enforcement use of its DNA Services.
🔒 Privacy Reminder
Privacy settings and policies can change. Always review the current policy and settings of the DNA provider before testing or uploading genetic data.
Take Your Research Further on Genetic Voyage
Frequently Asked Questions About DNA Matching
🎯 Key Takeaway
DNA matching is most powerful when genetic evidence and traditional genealogy work together. Use shared DNA to find clues, then use family trees, shared matches, historical records, and other evidence to discover how you may be related.
Final Thoughts
Understanding how DNA matching works gives you a foundation for genetic genealogy. A DNA match can open a door to a previously unknown relative, but the real research begins when you investigate the evidence behind the match.
Start with the amount of shared DNA, examine the available family-tree information, look for shared matches, and then test your theories against reliable historical records. With practice, DNA matching can become one of the most powerful tools in your genealogy research toolkit.
Sources and Further Reading
- ISOGG Wiki: CentiMorgan (cM) – Definition of the centimorgan, its relationship to recombination frequency, and its use in genetic genealogy.
- ISOGG Wiki: Autosomal DNA – Overview of autosomal DNA inheritance and its application in genealogical matching.
- ISOGG Wiki: Identical by Descent (IBD) – Definition of IBD segments and how they differ from identity by state.
- ISOGG Wiki: Identical by State (IBS) – Explanation of IBS segments and their relevance to small or distant DNA matches.
- ISOGG Wiki: Triangulation – Method for confirming a common ancestor by comparing overlapping IBD segments among multiple matches.
- ISOGG Wiki: Chromosome Browser – Description of chromosome browser tools and how they display shared DNA segments.
- ISOGG Wiki: Recombination – Explanation of how recombination creates random inheritance patterns.
- ISOGG Wiki: Genetic Distance – Definition of genetic distance for Y-DNA, mtDNA, and autosomal DNA comparisons.
- ISOGG Wiki: Y-chromosome DNA – Overview of Y-DNA testing, including STR and SNP analysis.
- ISOGG Wiki: Mitochondrial DNA – Overview of mtDNA testing and matrilineal ancestry tracing.
- ISOGG Wiki: Short Tandem Repeat (STR) – Definition of STRs and their role in Y-DNA testing.
- ISOGG Wiki: Genetic Genealogy – Definition of genetic genealogy and its combination of DNA testing with documentary evidence.
- NHGRI Talking Glossary: Centimorgan (cM) – Official definition of the centimorgan from the National Human Genome Research Institute.
- NHGRI Talking Glossary: Single Nucleotide Polymorphisms (SNPs) – Definition and significance of SNPs in genetic research.
- NHGRI Fact Sheet: Genetic Mapping – Explanation of genetic mapping and its role in locating genes on chromosomes.
- Thompson EA. Identity by descent: variation in meiosis, across genomes, and in populations. Genetics. 2013;194(2):301–326. – Peer-reviewed review of identity by descent, recombination, and their impact on genetic relationships.
- McVean GAT et al. The fine-scale structure of recombination rate variation in the human genome. Science. 2004;304(5670):581–584. – Study demonstrating that recombination rates vary extensively across the human genome, with hotspots occurring every ~200 kb or less.
- Bettinger B. Version 4.0! March 2020 Update to the Shared cM Project. The Genetic Genealogist. – Collaborative project providing observed shared cM ranges for nearly 50 genealogical relationships based on over 60,000 submissions. Source of the cM averages and ranges used in the 350 cM worked example.
- DNA Painter: Shared cM Tool – Interactive tool for exploring possible relationships from a shared cM amount, based on Shared cM Project data.
- Ball CA et al. AncestryDNA Matching White Paper. AncestryDNA, 2016. – Technical description of AncestryDNA's process for identifying identical-by-descent segments and estimating relationships.
- MyHeritage: How do I review a DNA Match? – Guide to reviewing DNA matches, including shared DNA, shared segments, shared matches, and triangulated segments.
- MyHeritage: What are the privacy options for my DNA data? – Overview of DNA privacy settings, including matching participation, shared segment sharing, and informed consent.
- Board for Certification of Genealogists: Genetic Genealogy Standards – DNA-specific standards for using genetic evidence in genealogical research, emphasizing the Genealogical Proof Standard.
🎯 Ready to Interpret Your Own Matches?
Put theory into practice with our free calculator and chromosome browser, or continue with the advanced triangulation guide.