By: Katy Rowe-Schurwanz

Learn about the inheritance pattern of autosomal DNA, the sample collection process, laboratory analysis, and result analysis for genealogical matching and ancestral population calculations.

Editor’s Note: This is part two of a seven-part series about what autosomal DNA is, what autosomal DNA can tell you, and how to apply autosomal DNA results to your genealogy. Continue reading the series here:

  • Autosomal DNA inheritance: Both paternal and maternal line contributions

    You inherit half of your autosomal DNA from each parent—one copy of each chromosome. Your parents inherited half of their autosomal DNA from each of their parents, your grandparents inherited half of their autosomal DNA from each of their parents, and so on. Because of this inheritance pattern, autosomal DNA can provide matches to any of your ancestral lines.

    When the autosomes are passed down from parent to child they go through a process called random recombination. This means while you’re getting 50% of what your parents inherited from their parents, it’s a random 50%—you’re not likely to inherit a perfect 25% from each of your four grandparents. You could inherit 10% of your maternal grandfather’s autosomal DNA and 40% of your maternal grandmother’s DNA.

    And if you have siblings, they will have inherited a different mixture of your parents’ autosomal DNA than you did.

    Autosomal DNA testing process

    Sample collection

    All of FamilyTreeDNA’s tests including the Family Finder are run off of samples collected with buccal swab kits. The FamilyTreeDNA collection kit contains two buccal swabs.

    Once you have placed your order, if this is the first test you have ordered from FamilyTreeDNA, we will mail out our DNA collection kit to you. Once you have returned your samples to us, we’ll send one to the lab for extraction and testing and place one in storage. If this is not your first test with FamilyTreeDNA, we will obtain your previously submitted sample from storage and send that to the lab for extraction and testing.

    Laboratory analysis

    Autosomal tests are run on chips in the lab that are comprised of selected SNPs. FamilyTreeDNA uses a custom Global Screening Array chip from Illumina that looks at about 700,000 SNPs from the autosomes, X chromosome, Y chromosome, and mtDNA. Because the main purpose of this chip is to determine autosomal results (matching, ancestral populations, etc.), the chips contain minimal Y-DNA and mtDNA SNPs.

    To keep up with new knowledge, changes in technology, and expanded reference populations, microarray chips like the Global Screening Array chip have been updated over time, and companies may have used various chip types over the years.

    Result analysis

    Before being processed for matching and myOrigins analysis, your data first goes through a process called imputation. Imputation expands your results by inferring results for additional locations that were not tested based on the results you do have. This information can be inferred because certain locations are typically inherited together. So if Position 1 and Position 2 on Chromosome 1 are typically inherited together, and if everyone always has the same allele for Position 2 as they do for Position 1, then if only Position 1 was tested on the autosomal chip, we can infer the result for Position 2 based on the result for Position 1.

    Because each testing company has used several different autosomal chips with different SNPs on them, imputation allows for matching across all SNP data sets across all chip types.

    Imputation also allows for matching across all SNP data sets across all chip types for both the Family Finder and the companies FamilyTreeDNA accepts autosomal transfers from, either currently or in the past.

    After imputation, files are analyzed for comparison to the tester database for matching and for comparison to our reference populations to calculate your myOrigins and ancientOrigins percentages. Once that analysis is complete, your results are uploaded to your FamilyTreeDNA account and you receive a notification that they’re ready.

    In part three, we will cover how to interpret your Family Finder test results. Make sure to subscribe to our blog to receive part three straight to your inbox.

Headshot of Katy Rowe-Schurwanz - Product Manager at FamilyTreeDNA

About the Author

Katy Rowe-Schurwanz

Product Manager at FamilyTreeDNA

Katy Rowe-Schurwanz has always been interested in genealogy, inspired by her maternal grandparents, who told her stories about their family and family history when she was little. After studying anthropology and history in college, she joined FamilyTreeDNA in 2015 and became the Trainer for Customer Support. Katy created and improved training processes and was fundamental in the creation of the Big Y Specialist team. In September 2021, she became Product Manager and has focused closely on improving FamilyTreeDNA’s genetic genealogy products.