By reviewing your options for a direct DNA test to the consumer, the options can be overwhelming. Between the different companies available, the test methods used and the services provided, it can be difficult to choose a company and plan with confidence. In terms of test methods alone, there are several different approaches different companies take to analyze their genetics. In general, companies tend to analyze up to 3 different parts of their genetic code. Most companies test their autosomal chromosomes. These chromosomes represent most of your DNA. Representing 22 of the 23 chromosomes.
The 23rd chromosome is the Sex Chromosome, and contains two forms: X and Y. females have a pair of X chromosomes, while men have an X and a Y. Because the y is always transmitted from the father, scientists can use genetic markers on the y chromosome to better understand the ancestry of a person Due to the fact that both the men and the women carry one X chromosome, a maternal line can’t be interpreted by studying only the x chromosome. In fact, many companies analyze the X-chromosome with the rest of the autosomal chromosomes.
Instead, laboratories rely on mitochondrial DNA (ADNmt). This form of DNA resides within the mitochondria, small organelles that produce energy for your body. These organules are only transmitted through an egg or egg. Therefore, his ADNmt test comes only from his mother and grandmother. Scientists can use ADNmt to study their maternal ancestry.
What are the Most Accurate Methods?
Although this is a simple question, it is a complicated answer with several parts. In the broadest sense, the above three test methods are as valid as the next one. These three “methods” simply refer to testing different parts of the DNA code. However, how that code is tested is quite similar among all DNA testing companies.
To test large amounts of DNA quickly, a laboratory cannot “read” each sequence in the DNA. Human DNA contains approximately 3 billion base pairs of individual nucleotides. To read and accurately identify each of these would take too long.
Instead, laboratories commonly seek SNPs, or single nucleotide polymorphisms. While most of their DNA is identical to almost all others, small parts of some genes have developed mutations and changes over time. These changes are often just a single pair of nucleotides in the code over 3 billion. However, a gene with several unique SNPs can be positively identified as one of several alleles (or versions) of the gene. Different alleles work differently, producing slightly different proteins that can affect the functions of your cells or body as a whole.
To identify these SNPs, labs use SNP chips. These small devices can test large amounts of DNA for specific SNP sequences. If an SNP is found, it is linked and identified by computer scans. These chips may contain information from hundreds of thousands of SNPs. The more SNPs contains a chip, the more SNPs per gene and the greater the chances of a real positive. A false positive may occur if a company does not use enough SNPs to identify a specific allele.
Below is a graph with several of the leading genetic testing companies, the SNP chip they use, and the number of SNPs they test for. This data was compiled by the International Society of Genetic Genealogy Wiki.
|Company||23andMe||Family Tree DNA’s Family Finder Test||Ancestry.com’s AncestryDNA test||National GeographicGenographic Project Geno||MyHeritage|
|SNP Chip||Illumina GSA Chip||Illumina OmniExpress||Illumina Chip||Illumina OmniExpress||Illumina OmniExpress|
|Autosomal SNPs Tested||630,132||690,000||637,639||700,000||702,442|
At first glance, you will notice that all major companies use SNP chips from the same source: Illumina. Many of these companies have customized Illumina chips, which look for different SNPs than their competitors. While it may seem like a great variety in the number of SNPs tested, in the context of billions of nucleotide pairs, the difference between companies is not so much.
You’ll also notice that some companies test only autosomal DNA. While this may not necessarily makes them less precise, we can extract much of the mitochondrial DNA and the DNA of the chromosome Y. These sources of DNA are changing relatively slowly with time, and may be related to large movements of the human population, known as haplogroups.
That said, the National Geographic Geno project will probably be one of the most accurate and comprehensive tests provided. Not only test the SNPs more autosomal, but they also test most of the SNPs of Mtdna and SNPs of DNA Y. This probably will provide a more complete picture of your DNA. 23and I would take a second strong, with Ancentry.com getting a tight third. Remember, as companies upgrade their chip technology and DNA processing speed increases, testing is likely to become much more accurate.
What Can the DNA Test Results Tell Me?
More important than how many SNPs a company tests for are the scientific validity of the results they present. For example, being a carrier of the cystic fibrosis gene is easily probable, and is valid if the testing company uses enough SNPs to identify the gene. However, if a company suggests eating a certain type of cheese based on its “genetic profile”, the scientific evidence is deficient.
In fact, the guidelines for so-called Nutrigenomics, or diet-tips based on your genetics, are still in your infancy. At present, the industry is largely regulated by internal guidelines established within the companies themselves. Other scientists have criticised the industry for not following Test practices rigorous enough to be meaningful. One study found at least a 40% error rate in false positive reports.
This means that 40% of the time companies reported that the patient has an allele that they did not. The authors of the study emphasize the confirmation of their results with their doctor in a more clinical and rigorous environment. This is especially true in cases that may affect your health.
That said, the FDA (Food and Drug Administration) has authorized the use of these tests for diseases such as Parkinson’s, Alzheimer’s, celiac disease, and others that may have a genetic component. While this increases confidence in the testing methods of some companies, remember that the results of a direct genetic test to the consumer can be very flawed. Any actual medical genetic counseling should be sought through a health care provider.
The CDC also provides an import resource to determine the validity of genetic test results. In their knowledge base of Public Health Genomics, they have classified and classified various genetic conditions with their scientific validity. Diseases such as cystic fibrosis and ovarian cancer, which have clear and probable genetic components, are classified in Level 1.
Level 2 is reserved for conditions that have links to certain genes, but the evidence is unclear. Many conditions fall into this category, such as acne, overactive bladder, and arthritis. While these diseases may have been related to some genes, there is no clear evidence linking these diseases solely to genetics. Companies will often include these tests in a genetic assessment regardless of their lack of scientific rigour.
Level 3 is reserved for the least admitted tests. This includes testing for things like depression, diabetes, and resistance to common diseases. While scientists have identified some links between genetics and these areas, there is really no evidence linking these ailments to genetics. For example, hereditary tests of breast and ovarian cancer through genetic screening are found at Level 3. While your personal genetics may play a role in cancer, checking your genetics is not a safe method of detecting cancer. You should still receive regular health checks from your doctor.
So, Should I Get a Direct DNA Test to the Consumer?
If you want to know more about your personal genetics and have become familiar with the current limitations of genetic testing, go ahead!
Just remember, not all tests are accurate or valid. Any company can present you with disastrous or dramatic results. Use resources such as the CDC and the FDA to judge the validity of the tests you are receiving. If you are concerned about your results, consult a doctor. Also, remember that your genes are just a simple plan. Increasingly, scientists are coming to understand that genetics is only a part of Health. The other part is lifestyle, diet, and exercise. These components of your life play an equal, if not greater, role in your overall health.