The Big-Y Testing Tool

The Big-Y tool is a next-generation (NextGen), direct paternal lineage test to explore deep paternal ancestry. It inspects thousands of known branch markers and millions of positions on the Y-chromosome where there may be new terminal (branch) markers. Big-Y is not commonly used for genealogy but it may provide additional information of a specific lineage since it allows both in-depth STR and SNP analysis. It is intended for expert researchers with an interest to advance genetic science but for our purpose we hope it may eventually help identify the ancestors of the STURDEVANT patriarchs.

Here is a link to the relevant FTDNA description, Introduction to the Big-Y. The output report of the Big-Y test is a large file generally around 500Mb and ending in the file extension “.bam.” It is commonly referred to as a “BAM” file. FTDNA does not perform BAM file analysis but matching and related functions are available on the myFTDNA home page.

Although not stated, the FTDNA Big-Y product also includes additional, non-Y-DNA information. Other included tests are similar to the FTDNA “Family Finder” (FF) and a “Full Mitochondrial Sequence” (FMS). However, unfortunately, the latter two results which are contained in the BAM output file, are not available through the FTDNA member user account (as are the separately paid tests). The FTDNA Big-Y test is now replaced by the very similar “Comprehensive Genome.” Current cost at FTDNA is $549. Similar tests are available at other companies.

Here are some relevant definitions that may be useful when reviewing Big-Y results:

  • Ancestral vs. Derived – When a SNP is in the derived state, a mutation has occurred. When the SNP is not in the derived state (i.e., no mutation), it is ancestral (unchanged).
  • Genotype – the base allele value at a given position.
  • Negative SNP – a SNP without a mutation; also called an ancestral SNP.
  • Known SNP – any SNP on the list of known SNPs against which Big-Y data is compared.
  • Match – For the Big-Y, a person is considered a match if they have four or fewer differences in SNPs.
  • Novel SNP – a positive SNP that is not on the list of known SNPs. The SNP may or may not be unique to an individual. Men in related lineages may share some novel variants.
  • Position – The location of the SNP or STR on the chromosome.
  • Positive SNP – a SNP with a mutation; also called a derived SNP.
  • Private SNP – a known or novel SNP not matched by another person, i.e., a single occurrence of the SNP.
  • Reference – the base indicated by the GRCh37 human reference genome, which is maintained by the Genome Reference Consortium. The following values are possible: A (Adenine), C (Cytosine), T (Thymine), G (Guanine).
  • SNPsingle nucleotide polymorphism; a variation in a single nucleotide that occurs at a specific position in the genome,
  • STRshort tandem repeats are short sequences of DNA that are repeated.
  • STR value – the number of repetitions for a specific STR.

Here is a link to the full, interactive SNP report at Each green SNP indicates a positive (+) test result (click to see). There are no positive results  below L22, therefore, the clade is indicated as L22*. Negative (-) results are not shown for the obvious reason.

Genetic Distances of nearest STR matches (interestingly, 5 of 9 originate in northern europe):

More information relating to the YFull analysis may be found at the below links.

The following Big-Y test results are available only to logged-in STURDEVANT DNA Project members. As more tests become available, results will be used for analysis of deep STURDEVANT ancestry:

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