How does DNA testing work (Complete guide)

Summary

This video explores how consumer DNA testing works, examining companies like 23andMe and AncestryDNA. It delves into how these tests identify genetic ancestry through single nucleotide polymorphisms (SNPs) and microarray technology. While ancestry results can be imprecise due to historical migration, family relationships are more accurately identified. The video also critiques the limitations of disease risk testing, with insights into how mutations might only increase disease likelihood, not guarantee it. Finally, it discusses newer, more comprehensive gene sequencing technologies that offer deeper insights, but also raise challenges in interpreting the vast genetic data.

Takeaways

• 😀 DNA testing helps determine genetic ancestry, disease risks, and traits like earwax type.
• 😀 Consumer DNA tests, like those from 23andMe and AncestryDNA, rely on microarray technology to analyze genetic samples for SNPs (single nucleotide polymorphisms).
• 😀 SNPs are variations in DNA that can indicate genetic differences between individuals and populations, helping to determine ancestry.
• 😀 The accuracy of ancestry testing is limited because human migration has been so widespread that establishing distinct populations is challenging.
• 😀 The results of ancestry testing can be inconsistent between different companies and even among identical twins tested by the same company.
• 😀 Consumer DNA tests are generally accurate in identifying familial relationships, but the genetic link weakens as the generations get further apart.
• 😀 Testing for disease risk is based on specific SNPs, but it’s not definitive; having a SNP associated with a disease doesn't guarantee developing the condition.
• 😀 The FDA allows 23andMe to report on certain disease-related genetic mutations, but these reports only provide risk factors, not definitive diagnoses.
• 😀 Raw genetic data from consumer tests may contain false positives, leading to potential misinterpretation when used by third-party services or untrained individuals.
• 😀 Newer sequencing technologies provide more comprehensive analysis by sequencing entire genes or genomes, revealing mutations that microarrays might miss.
• 😀 The sheer amount of genetic data generated by sequencing technologies makes it challenging to interpret, as many variants have no known implications for disease.

Q & A

How do DNA testing companies analyze a DNA sample?

DNA testing companies like 23andMe and AncestryDNA use microarray tests to analyze a DNA sample. These tests look for Single Nucleotide Polymorphisms (SNPs), which are variations in the DNA that can indicate certain traits or health risks. The DNA is amplified, cut into smaller pieces, and then hybridized onto a microarray chip that has known sequences of DNA. The binding of the sample DNA to these known sequences is then analyzed to identify genetic variations.

What is a Single Nucleotide Polymorphism (SNP)?

A Single Nucleotide Polymorphism (SNP) is a variation at a single position in the DNA sequence. SNPs can affect how genes function and may influence traits like disease risk or physical characteristics. DNA testing companies focus on these variations to gather information about your ancestry or health risks.

Why is ancestry testing through DNA samples often inaccurate?

Ancestry testing can be inaccurate due to several factors. Firstly, the reference populations used for comparison are not always representative of the historical populations due to migration and mixing of genes over time. Additionally, it is impossible to compare modern DNA to ancient populations that lived hundreds of years ago. As a result, companies may give rough estimates that are prone to errors, especially when reporting percentages for specific regions.

How do DNA testing companies determine genetic ancestry?

DNA testing companies compare your DNA sample to reference populations, which are groups of individuals with known ancestral backgrounds from specific geographic locations. These populations are studied to identify common genetic variations. By comparing the SNPs in your DNA to these reference populations, the company can estimate your genetic ancestry and where your ancestors may have lived.

Why do identical twins sometimes get different ancestry results?

Identical twins may receive slightly different ancestry results due to the way the data is analyzed. Even though their DNA is nearly identical, small differences in the data or slight variations in how the analysis is conducted can lead to differing results. This can happen because of the complex statistical methods used to interpret the results.

What is the problem with the ancestry percentage results reported by DNA testing companies?

The ancestry percentage results reported by DNA testing companies are often imprecise. Companies rely on reference populations, but human migration over centuries makes it difficult to define accurate genetic boundaries. Moreover, the results are often presented with a degree of uncertainty, which means percentages can be misleading, especially when they are reported for specific countries or regions.

What does it mean when a DNA test is FDA-approved, like 23andMe's health reports?

FDA approval for a DNA test, like the health reports offered by 23andMe, means that the test has been reviewed and deemed safe to provide genetic risk information for specific diseases. However, FDA approval only covers certain conditions, and the report is not a diagnostic tool but rather an indicator of genetic predisposition to diseases like breast cancer or Parkinson's. The test only reports known mutations and cannot provide a definitive diagnosis.

What are the limitations of using DNA test results to predict diseases?

DNA test results predict disease risk, not certainty. Even if a person has a genetic mutation linked to a disease, it doesn't mean they will definitely develop it. Disease risk reports are probabilistic, meaning they show an increased likelihood but not an inevitable outcome. Additionally, many other factors, such as environment and lifestyle, influence disease development.

Why is it not recommended to use raw DNA data for health risk analysis?

Using raw DNA data for health risk analysis is not recommended because the raw data may contain errors, such as false positives or misinterpreted results. Raw data is often incomplete or unvalidated, and the information may be difficult for an untrained person to interpret accurately. Misinterpretation can lead to unnecessary panic or false reassurance.

What are the advantages of sequencing technologies over microarray tests in gene testing?

Sequencing technologies offer more detailed and comprehensive insights than microarray tests. Sequencing can analyze the entire genome or specific regions of genes, detecting mutations that may not be included in microarray tests. Unlike microarrays, which only check for known variations, sequencing can identify new or rare mutations and provide a clearer picture of genetic health risks. However, sequencing generates large amounts of data that require professional analysis.