Do more Y-DNA STR markers improve the quality of matches’ information?

You should test more Y-Chromosome DNA short tandem repeat (STR) markers when you wish to compare additional markers against others with similar results. They will refine your matches for genealogical purposes. It does not increase the number of generations traced by a Y-DNA STR test, but rather reduces the range of generations in the time to a common ancestor with your match.

Testing additional STR markers can also help refine the matches in the Y-DNA – [...]

Don’t we all go back to Africa?

Yes, all of our Y-Chromosome lineages trace back to a common ancestor who lived in Africa at least 115,000 years ago. Some lineages migrated out of Africa; others remained.

This map shows each of the major (backbone) paternal haplogroups’ paths out of Africa.

(+ View Y-DNA Migration map)

The path that our ancestors took tells a story about human history. Testing your relatives’ and your own DNA can help you understand both the diversity and commonalities of [...]

How does the infinite allele comparison method work for palindromic markers?

For palindromic markers, the infinite allele method counts a difference for two types of changes: a mismatch and a copy number change. Mismatches are any time the compared markers do not match. For example, the first man might have DYS464 = 14-15-15-16 and the other man might have DYS464 = 14-15-16-18. This counts as a single difference toward the two men’s genetic distance. Palindromic copy number changes are when one person has more copies [...]

How is genetic distance calculated for NULL values?

For Y-Chromosome DNA STR matching, genetic distance is calculated as a single NULL causing event. The NULL value causing event is treated as a single step event with a genetic distance of one. The one exception is for the STR marker DYS439. The difference there between a value of say 12 and a NULL value is calculated as a genetic distance of 12.

How many generations does a Y-Chromosome DNA (Y-DNA) STR test trace?

Y-Chromosome DNA (Y-DNA) tests trace both recent and distant generations. The number of generations traced by a Y-Chromosome DNA test depends on the type of test taken, short tandem repeat (STR) or single nucleotide polymorphism (SNP).

STR tests are able to trace a male lineage within genealogical times and into historic times. Your genealogical connections will be shown on the Y-DNA – Matches page of your myFTDNA account. The Y-DNA – Ancestral Origins page of [...]

Why do I have more than one result for an STR value? What is a multi-copy STR marker?

A multi-copy STR marker is one where there are multiple versions of the same STR in different locations on the Y-Chromosome. Each STR copy changes independently. Therefore, it is typical to have different values for each copy.

For example, DYS385 usually has two copies.

What is the likelihood of a non-paternal event or false paternity?

We believe that the rate of unannounced adoption or false paternity is about 1-2% per generation. When confirming your lineage, we recommend that you test yourself and your most distantly related male ancestor to verify the line back to the common male ancestor.

What is different about the STR markers DYS389i and DYS398ii? Why is my DYS389-2 result at Family Tree DNA different from the Genographic Project?

The Y-Chromosome STR Y-Chromosome DNA (Y-DNA) marker DYS389 is a single STR marker that has four parts: m, n, p, and q.

At Family Tree DNA we have two tests for DYS389. The first test looks at the first part two parts of marker DYS389 (m and n). This is what we call DYS389-1. The second test looks at all four parts of DYS389 (m, n, p, and q). This is what we call DYS389-2. [...]

What does each short tandem repeat (STR) marker mean?

By themselves, Y-Chromosome DNA (Y-DNA) short tandem repeat (STR) markers from a Y-DNA test do not have any particular meaning. The value of testing Y-DNA STR markers comes from creating a Y-DNA signature (haplotype) with them and comparing that Y-DNA signature to others in a database. They are useful for genetic genealogy because your Y-DNA signature distinguishes your paternal lineage from others. They can then be used with Family Tree DNA’s comparative database to [...]

What do the DYS, DYZ, and DYF prefixes on Y-DNA STR names mean?

The DYS, DYZ, or DYF prefixes are part of the scientific name for a short tandem repeat (STR) found on the Y-Chromosome. STR markers are named according to guidelines published by the HUGO Gene nomenclature committee. For Y-DNA STR tests:

D stands for DNA.
Y stands for Y-Chromosome.
S, Z, or F stands for the complexity of the repeat segment.

S is a unique segment.
Z is a number of repetitive segments at one site.
F [...]

Why don’t my Y-Chromosome DNA (Y-DNA) test results show me percentages?

Your Y-Chromosome DNA (Y-DNA) test results cannot be used to indicate your percentage of DNA from different ancestral groups. This is because tracing your Y-DNA line only leads to one origin.
Y-Chromosome DNA Inheritance

1
2
3

Father’s Father

Father

Father’s Mother

You

Mother’s Father

Mother

Mother’s Mother

Y-DNA does not provide a breakdown of various ethnic origins from your other ancestral lines.

You received your Y-DNA from your father who got it from his father, who got it from his father, and so [...]

If somebody doesn’t match me at 12 markers, how can they match me at a higher testing level?

Aside from their having matching turned off at the Y-DNA12 level, someone might match you at a higher testing level but not Y-DNA12 because the genetic distance is more than the amount allowed for Y-DNA12 but not the higher level.

For example, kit B193 has mismatches with kit B175 at DYS393 and DYS385. Each mismatch has a genetic distance of one for a total genetic distance of two. This is more than the amount allowed [...]

If two men share a surname, how should the genetic distance at 111 Y-Chromosome STR markers be interpreted?

In cultures where surnames are passed from father to son, there is additional evidence beyond a DNA match that two men who share a surname are related. Y-Chromosome DNA (Y-DNA) test results should be interpreted based on both this information and the actual results.

Genetic Distance
Relationship
Interpretation
Related in This Number of Generations or LESS

Confidence

50%
90%
95%
99%

0
Very Tightly Related
A 111/111 match indicates a very close or immediate relationship. Most exact matches are [...]

If two men share a surname, how should the genetic distance at 67 Y-Chromosome STR markers be interpreted?

In cultures where surnames are passed from father to son, there is additional evidence beyond a DNA match that two men who share a surname are related. Y-Chromosome DNA (Y-DNA) test results should be interpreted based on both this information and the actual results.

Genetic Distance
Relationship
Interpretation

0
Very Tightly Related
A 67/67 match between two men who share a common surname (or variant) means they share a common male ancestor within the genealogical time [...]

If two men share a surname, how should the genetic distance at 37 Y-Chromosome STR markers be interpreted?

In cultures where surnames are passed from father to son, there is additional evidence beyond a DNA match that two men who share a surname are related. Y-Chromosome DNA (Y-DNA) test results should be interpreted based on both this information and the actual results.

Genetic Distance
Relationship
Interpretation

0
Very Tightly Related
A 37/37 match between two men who share a common surname (or variant) means they share a common male ancestor. Their relatedness is extremely close [...]

If two men share a surname, how should the genetic distance at 25 Y-Chromosome STR markers be interpreted?

In cultures where surnames are passed from father to son, there is additional evidence beyond a DNA match that two men who share a surname are related. Y-Chromosome DNA (Y-DNA) test results should be interpreted based on both this information and the actual results.

Genetic Distance
Relationship
Interpretation

0
Related
A perfect 25/25 match between two men who share a surname (or variant) means they likely share a common male ancestor within the genealogical time frame. The [...]

If two men share a surname, how should the genetic distance at 12 Y-Chromosome STR markers be interpreted?

In cultures where surnames are passed from father to son, there is additional evidence beyond a DNA match that two men who share a surname are related. Y-Chromosome DNA (Y-DNA) test results should be interpreted based on both this information and the actual results.

Genetic Distance
Relationship
Interpretation

0
Related
A perfect 12/12 match between two men who share a common surname (or variant) means they likely share a common male ancestor within the genealogical time frame. The [...]

Expected Relationships with Y-DNA STR Matches

The expected relationship between you and your Y-Chromosome DNA (Y-DNA) match is dependent on both the number of markers you have tested and the genetic distance. The chart below shows the interpretation of your relationship at each testing level (Y-DNA12, Y-DNA37, etc.) for relevant genetic distances.

For example, if you and your match have both tested at the Y-DNA37 level and are a 36/37 match this is a genetic distance of one. You are then [...]

Y-DNA Genetic Distance

When talking about two or more Y-Chromosome STR (short tandem repeat) haplotypes, genetic distance is the total number of differences, or mutations, between two sets of results. In general, it is found by summing the differences between each STR marker.

For example, kit B291 and B125 have allele values of 29 and 28 respectively at DYS389-2. This is a difference of 1 {29-28= 1}. Because this is the only difference in their Y-DNA12 profiles (haplotypes) [...]

Y-DNA Step-mutations

When comparing the results of Y-Chromosome STR (short tandem repeat) tests, the difference between the two values at a marker is the Y-DNA genetic distance or the step-mutation count. That is, a one-step mutation means that the count for a single STR has changed by one. A two-step mutation means that the count for a single STR has changed by two.

For example, when comparing kit B193 and kit B173, the STR marker DYS393 has [...]

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