Why Do DNA Test Results Vary Between Testing Companies?

Introduction

When individuals undergo DNA testing to learn about their ancestry, they often find discrepancies in the results across different testing companies. For instance, one DNA testing site might show a user as predominantly Ashkenazi Jewish, while another may show very little Ashkenazi Jewish ancestry. This article will explore the reasons behind these variations and what one can do to better understand their results.

The Variability of DNA Ancestry Results

The differences in DNA ancestry results can arise from several factors, including the methodologies used by different testing companies, the reference populations they use, and the algorithms they employ to interpret genetic data. Here are some key points to consider regarding your situation:

Reference Populations

Each DNA testing company has its own set of reference populations that they compare your DNA against. If one company has a more diverse or extensive reference database for Ashkenazi Jewish ancestry, it may identify that ancestry more readily than another company with a different or smaller database.

Algorithm Differences

The algorithms used to analyze and interpret the DNA data can vary significantly between companies. Some may have more sophisticated models for detecting specific ancestries, while others might be more conservative in their estimates, leading to differences in the reported percentages of various ancestral groups.

Depth of Testing

Different companies may use varying depths of sequencing or different markers in their tests. Some companies might focus on autosomal DNA, while others might also consider mitochondrial or Y-DNA. This can lead to varying interpretations of ancestry, as each type of DNA provides a different aspect of an individual's genetic history.

Updates and Improvements

DNA testing companies frequently update their algorithms and reference databases. If one company has recently made significant improvements or updates, it might show different results compared to another company that hasn't updated its database or algorithms in a while. These updates can lead to more accurate and consistent results over time.

Ancient vs. Recent Ancestry

Your friend's suggestion about ancient results could be relevant. Some testing sites may emphasize ancient lineage connections, which can lead to a different interpretation of your ancestry. More modern testing might focus on recent genealogical connections, explaining the lower percentage of Ashkenazi Jewish ancestry reported by Ancestry.

Genetic Variability

Individual genetic variation can also play a role. Even within the Ashkenazi Jewish population, there is a range of genetic diversity. Depending on your specific ancestry, one test might pick up on that more than another, leading to variations in the reported results.

What Can You Do?

To better understand your results, consider the following steps:

Review Methodologies and Reference Populations

Review the methodologies and reference populations used by each company. Understanding how each company approaches ancestry testing can provide insight into why your results vary.

Check for Updates and Changes

Look into whether either company has provided updates or changes to their ancestry reports since you received your results. Companies that frequently update their methods and databases may show more consistent and accurate results.

Re-Testing with Different Services

Exploring the possibility of re-testing with a different company or using more than one service for a broader perspective on your ancestry can help you get a more comprehensive understanding of your genetic history.

If you're particularly interested in your Ashkenazi Jewish heritage, it may be helpful to consult with genetic genealogists who can provide more personalized insights based on your results.

Conclusion

Understanding the discrepancies in DNA ancestry results across different testing companies requires knowledge of various factors, including reference populations, algorithms, testing depths, updates, and genetic variability. By considering these factors and taking proactive steps to understand your results, you can gain a more complete insight into your genetic history.