The centiMorgan (cM) values for DNA segments are measurements of how likely the segment is to recombine as it passes from parent to child. Segments with higher cM values have a greater probability of recombining in any one generation. Therefore, [...]
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The Family Tree DNA bioinformatics team works with centiMorgan (cM) data from the International HapMap project. Current knowledge of centiMorgan values across the human genome comes from the International HapMap project testing. The project tested father-mother-child trios from global population [...]
Yes. Limitations in the number of global populations used and the number of samples tested in the International HapMap recombination rate studies limit what we know. SNP values at 12 locations in sequence Mother G A T A G A [...]
The recombination rate across the human autosomal genome is highly variable. Therefore, DNA segments that are the same number of base pairs long may have much different centiMorgan (cM) values depending on their location.
If two people share part of the same DNA segment with me, will the centiMorgan value for each segment be proportional to how long the segments look?
Overlapping DNA Segments cM Matching on Chromosome 1 Match 1 Match 2 Non-Match 20.5 7.6 No. Part of a matching DNA segment may have a higher or lower centiMorgan (cM) value than the segment's average. One of your matches will then [...]
Is it more significant if two of my matches have identical start and stop points than if the segments simply overlap?
No. When two of your matches' DNA segments share exact start and stop points, it is not more significant than when they simply overlap. There are two reasons for this. Both are due to current limitations of microarray chip technology. [...]
No. The Family Finder software does not use mitochondrial DNA results for matching or relatedness calculations. The Family Finder program uses only the autosomal SNP (single nucleotide polymorphism) test results from the Family Finder microarray chip.
No. The Family Finder software does not use Y-chromosome DNA (Y-DNA) results for matching or relatedness calculations. The Family Finder program uses only the autosomal SNP (single nucleotide polymorphism) test results from the Family Finder microarray chip.
I used a third-party tool to analyze my and a relative’s results. They are different from my Family Finder results. Why is this?
When you compare two people's Family Finder results using third-party tools, it is common for there to be small differences. The FamilyTreeDNA Family Finder program uses a proprietary set of calculations to evaluate shared DNA segments and to determine relationships. [...]
The closeness of a mitochondrial DNA (mtDNA) match depends on the matching level. Matches at higher levels are more likely to be recent. The table below shows the expected time to a common ancestor with your exact matches. This time [...]
Yes. It is possible that a SNP will back mutate (change back). However, SNPs are slow changing. Thus, back mutations are uncommon.
The Family Finder's relationship ranges cover most possible relationships between two people. It takes into account several factors. These include the total number of shared DNA segments (blocks) and the total number of centiMorgans (cM). For the immediate and close [...]
Are there any exceptions or special cases in how our DNA is inherited that would affect my predicted relationship and range?
Yes. There are exceptions to the way inheritance normally works. One example is a type of mutation called an inversion. In an inversion, a segment of DNA has detached and then reattached in the reverse direction. The segment is therefore [...]
Yes, a higher number of compared Y-DNA STR markers does increase the power and accuracy for Time to Most Common Ancestor (TMRCA) calculation. However, there are diminishing returns after a certain number of markers. For exact matches who share a surname, [...]
The microarray chip used for Family Finder tests about .024% of your autosomal DNA.
The Y-chromosome DNA (Y-DNA) results chart headings are color coded in two ways. First, each testing level (Y-DNA1-12, Y-DNA13-25, Y-DNA26-37, Y-DNA38-67, and Y-DNA68-111) is coded with a different shade of blue. Second, the STR (short tandem repeat) markers that have faster mutation [...]
Bob, John, and I have the same Genetic Distance. However, when compared, we have different probabilities for sharing a common ancestor, for example, within eight generations. Why?
FTDNATiP™ uses both the number of mismatches and the mutation rates of individual markers in calculations. This means that although two men may have the same number of mismatches, they may not have the same predicted Time to Most Recent [...]
Using Family Finder results for genealogy is more challenging for individuals of Jewish ancestry because of a lack of genealogical records, surname changes, and frequent intermarriage. The lack of genealogical records means that finding the connection with even a third cousin [...]
Family Finder detects your near and distant cousins by comparing your autosomal DNA with that of other Family Tree DNA customers. If two people share identical segments of DNA, they may share a recent ancestor. When the Family Finder program finds matching [...]
Are Y-chromosome DNA (Y-DNA) SNPs ever related to recent times and genealogy? Are they always for historic periods and more ancient ancestry?
Y-chromosome DNA SNPs (single nucleotide polymorphisms) are not always from anthropological or even historic times. Some Y-chromosome DNA SNPs are restricted to a single family that is related in genealogical times (one to 15 generations). These are family SNPs or [...]