The Issues With Accuracy of At-Home DNA Tests

Home Biology The Issues With Accuracy of At-Home DNA Tests

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By Trista - April 18, 2020

Have you been thinking about your family history and wondered if there was a way you could find out more about yourself? You probably thought your only option was to start researching and creating a family tree.

The good news is that you aren’t going to have to sift through the archives, and science can make this process a lot easier and faster for you. It’s called a DNA test. All you have to do is spit into a tube and send it to the lab.

Sending Your Swab To The Lab

The Issues With Accuracy of At-Home DNA Tests — *The first step in the process is to send your swab to the lab for DNA testing. Photo Credit: Dusan Petkovic/Shutterstock*

Once your DNA swab has gone off to the labs, you’ll have to wait a few weeks for the results. Another reason for DNA testing could be that you want to know more about yourself and not just your family history. Perhaps you want to learn more about your health.

It is known as DNA sequencing. In essence, this is looking at the order of the letters that make up your DNA. These letters are known as nucleotides and are the chemicals that create what is known as your DNA.

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An Alphabet In Your Body

This sequence isn’t as long as the alphabet of letters, in any case. There are only four. These letters are A, C, T, and G. They stand for adenine, cytosine, thymine, and guanine. When these letters are combined, they make up your genetics, which communicates to your body.

It tells your body what molecules it should be making. Did you know that this runs about 6 billion letters long? Your story is not a short novel; it has sequel after sequel. With each strand, some portions are called sequences.

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Decoding Your Genetics

When looking closer at these letters and their order, scientists can decode your genetic code. Every individual has a different order. What scientists can also do is compare the order of the letters in one DNA to someone else’s.

Even people who are part of the same family will have different letter sequences. It might seem simple, but it couldn’t be further from that. When letters are moved around, the gene meaning is altered, which changes the protein that is being made.

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The Effect Of Changes In Your DNA

When a change is made, it can contribute to things such as what color eyes you have and also your height. Different combinations also make you a higher or lower risk for certain diseases compared to someone who has another sequence in their DNA.

When you compare your DNA with someone else’s, you will be able to see just how closely related you are to that person. There are so many options out there for DNA testing and different reasons for why you want to test.

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Testing Your Pet’s DNA

You even have the option to test the DNA of your dog and cat. However, are all DNA tests equal to each other? No, they aren’t. You will need to decide on the purpose of your DNA discovery and then decide on the company.

As someone getting their DNA tested, you need to do your research to see the level of testing the company is capable of completing. DNA testing companies generally offer three main types of tests. It’s up to you to decide what you want out of it.

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Your First DNA Discovery Option

The first option is the whole genome sequence. This process can capture all of your six billion nucleotides in a genome. It will offer up your complete set of genes. The company that you have chosen will go through every single letter in your DNA.

It’s easy to miss some letters when you are working on something like this. When you are using whole-genome sequencing, it will not be able to detect if large chunks of DNA are missing or if it has been rearranged. What else can it miss?

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You May Need A Doctor To Recommend You

It might not also be able to see when a DNA section has been repeated a few times. Nevertheless, if you want the most complete view of your genes, this is the one you need to choose. Some companies may request that you have a prescription from a doctor before you have it done.

The next kind of test is the one that will focus on the proteins. Even though your DNA contains so many letters, not all of the words that it creates will mean something.

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What Some Of Your DNA Sequences Are Responsible For

Some of the sequences in your DNA are responsible for making up proteins, and others control how often your other DNA sequences are used to make these proteins. Different sequences give instructions for the different molecules.

There are also, of course, sequences that technically do not say anything at all. In scientific terms, the exome is part of your genome that holds your protein-coding genes. How much of a person’s DNA does this makeup?

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Exome Sequencing And What It Offers

It only makes up between 1-2 percent of the person’s DNA. What does an exome sequencing offer to someone? Well, it does not give information on genetic changes that may have the potential to turn other genes on or off.

It also won’t show which genes won’t be used to make a protein. But just because you can’t see this doesn’t mean it won’t serve a purpose. Many of your genes have a purpose, even if they aren’t the ones that are producing proteins.

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The Minimalist DNA Testing

There is also a third type of test and is known as the minimalist approach to DNA testing. This test looks at SNPs. It is short for single nucleotide polymorphisms. The purpose of these tests is to search for single-letter mistakes in your genome.

For example, someone might have a C in the place where most people have the letter A. Scientists have been able to identify collections of SNPs and use tests called SNP chips or also can be called genotyping arrays.

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Testing Millions Of SNPs

For this, you will take a sample of the DNA and then check for a preset group of SNPs. Companies that do testing can test millions of SNPs at one time with these tests. Nevertheless, still, it is only a small amount of letters in your genome.

Companies such as 23andMe and Ancestry rely on SNPs tests to determine their human DNA results. Some companies do the same for your dogs, such as emBark and homeDNA. If you’re looking into your cat’s DNA, you can use the Wisdom Panel or Optimal Selection.

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You Can See If You Are More Prone To A Disease

Most of these tests can be done without the recommendation from a doctor, but there will be occasions when doctors request that patients have their DNA tested to see if there have been changes in specific genes.

It is useful to see if any alterations have been made to your DNA that make you more prone to a risk of disease. The tests will be able to determine if the DNA by that gene has made changes for that specific person.

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Learn About Your Ancestry

There was a time when DNA tests were mainly for health or paternity reasons. However, now it has become part of the current culture to know your history. Many companies are now branding themselves as “ancestry” services. They offer insight into who we are.

These tests allow you to go way back in your family history and see where you originate. As exciting as this is, do these tests work when determining the test subject’s ancestry? 23andMe uses algorithms to get their results.

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How The Algorithms Work

These algorithms use the string of letters as explained above and work with those to determine the results. While none of these letters are going to spell out exactly where you came from, thanks to the algorithm, they can find the meaning behind the letters.

These companies do keep their algorithms secret. Their computers and systems are excellent at being able to discover a pattern. Researchers say that scientists have known about these techniques for a very long time.

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They Need A Large Library Of Samples

How it works is that if a genetic anthropologist has a DNA sample, they can compare it to their library of other samples. Through this, they can understand which groups in their collection the sample is closely related.

When getting down to the nitty-gritty, your paternal ancestry is tracked thanks to the Y chromosome. It is what fathers pass to male descendants. For maternal ancestry, this is found in mitochondrial DNA, which is what a mother passes onto all their children.

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Piece By Piece

Where the real details come from are the 22 non-sex chromosomes, which are compared against very extensive libraries of information. How does this work? The algorithm will take an entire genome and receive little pieces.

For each piece that it takes, it will compare it to the reference data set. It will compare it to an entire list of probabilities, such as British and West African. This method is how you can understand the results of tests such as 23andMe.

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Your Results In A Percentage

These tests come back with a percentage result. It might say something like, “You are 31% British.” This figure means that 31 percent of your DNA pieces compared the closest to the 23andMe library, which is considered to be British.

However, the pitfall of this method is that the tests are only as good as the library of the company. They will need to have an incredibly extensive range of samples to compare yours to have an accurate result.

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The Size Of Sample Groups

These libraries aren’t public, so you aren’t able to pick your company based on how big its genetic library is. 23andMe does, however, have much information on European populations as this is its biggest sample group.

For information on Native American populations, they do not have as much as it is one of their least sampled groups. This notion means that their library will be able to tell you precisely what Jewish group you are from but will combine Native Americans into one general category.

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Making The Investment

So, now you have decided that you want to invest in finding out about your lineage through a DNA service such as 23andMe. It’s time to take a spit sample to send off to their laboratories for testing. How do you do this?

Some people find it challenging to produce the amount of saliva that is needed for this test. When you have ordered your test, make sure that you read the instructions very carefully and also any information on how to provide the saliva sample.

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It’s Time To Make Some Saliva

If you are finding it challenging to produce the amount of saliva, there are some ways to help increase the amount of saliva you are providing. One of these methods is to take your hands and place them on the outside of your cheeks.

You will then gently rub them, and this should stimulate saliva production inside your mouth. If that option doesn’t work for you, try to mimic a chewing motion with your mouth. Another incredible tip is to think about your favorite food.

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Imagine Sour Foods Like Lemons

If this still hasn’t got you salivating, then you can imagine sour foods like lemons or sour sweets. You could also try smelling them if you happen to have them in your kitchen. This service says that they do not recommend that you bite or scrape your cheeks.

The reason for this is that the cells in your saliva sample that will be analyzed by the company are your white blood cells and not the epithelial cells from your cheeks. These can get mixed in if you bite or scrape your cheeks.

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How To Collect Your Sample

When you are collecting your saliva sample, you need to collect it all within a time frame of 30 minutes. You need to funnel the contents into the tube straight away. It prevents the DNA from degrading over the waiting period.

If you wait longer than 30 minutes or delay releasing the buffer solution, your quality of the DNA could be compromised. Some people, however, have a condition in which their mouth is naturally dry or are on medication with this side effect.

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Releasing The Buffer

Instead of putting their saliva in first and then releasing the buffer, they will do it the other way around. The buffer will first be released into the tube and then topped up with saliva.

If you are unlucky enough to spill the buffer liquid, you will need to request a new kit from the company. In total, you need to be able to produce a one-half teaspoon of saliva. It is estimated that it took an adult between 5-10 minutes to produce this amount.

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Who Can’t Use DNA Tests

Are there any groups of people who aren’t able to use this type of DNA testing? Yes, some individuals can’t. There may be certain people who are currently undergoing medical treatment. It could affect their white blood cell count.

An example of this is chemotherapy. People who are undergoing chemotherapy have been advised that they should only do the test two weeks after their last treatment, or they can wait until their white blood cell count is normal.

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If You’ve Had A Bone Marrow Transplant

This restriction also applies to people who have received a bone marrow transplant. With this situation, it would be hard to discern whether the results were accurate on the DNA of the person wanting the test or from the donor.

Consumers are going crazy for these tests, and they may seem very exciting and informative, but how accurate are they? They can tell you what diet works best for your body, your preference for certain foods, and medical conditions.

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DNA Testing Advanced In 2003

The critical development happened in 2003. It was when the Human Genome Project was able to deliver the human DNA sequence fully. Advanced testing showed that technology was able to read DNA results at an incredible speed and an affordable cost.

This new tech has allowed it to become more popular and for people to use it for “fun” and not just for medical research. It increased the commercial interests from companies, and it became an excellent way for these labs to make money for the business.

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Two Issues From DNA Results

As exciting as the potential is, two issues could come from the results and their accuracy levels. First off, people are concerned with whether the sequencing has been done well. Generally, it is accurate, but there are cases of failure.

There was a company that wasn’t able to tell that the DNA sample was actually from a dog and not a human. Another analysis was done and found that 40% of variants that are related to specific diseases from genetic tests were false positives when the data was analyzed again.

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It Doesn’t Sequence Your Entire Genome

But, when you assume that the tests have been done correctly, there are still some errors that can happen because of differences between individual companies and their DNA databases that they are comparing your DNA to.

Most DTC genetic tests do not sequence your entire genome. Instead, they analyze positions in your DNA that are popular. There was one person who did DNA tests with a couple of different companies, and their results came out differently.

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Different Results From Different Companies

One company said that they did not carry a gene that is associated with red hair. The other company they sent their spit off to, said that they did. What does this tell us? One of the companies was analyzing variants of the gene that code for red hair.

What is the second concern? The Genome Wide Association Studies determine the positions of interest in DNA. When using a group of as many people as possible who have a shared trait such as red hair…

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It Only Offers A Probability

You then sequence their genes and look for specific places in their DNA that are the most similar to the group you are testing rather than a different population. With red hair, there are quite a few variants in the same gene that give someone ginger hair.

When it gets more to more complex traits in a person such as taste or exercise, there will be many variants. For this, they only offer a probability of why you have that type of behavior when measured against the population.

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Will You Have Blue Eyes Because Of Genes?

This concept can be seen when looking at eye color as well. Someone may have a gene variant that is considered to be popular when someone has blue eyes, but it is just a probability. You might end up with brown eyes, even with two blue-eyed genes.

Genetics is known as a probabilistic science. Some people are concerned with how these DNA tests offer to show their subjects their probability for specific medical conditions. You can discover more about the likelihood by researching punnet squares in regards to dominant and recessive genes.

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It’s Based On Your Lifestyle

It is still very likely that you will never develop this disease. This notion is influenced by your lifestyle as a whole and also just by chance. However, when it comes to checking at your ancestry, DNA is the best way to determine family relations.

It can show precisely who your siblings and parents are as well as reuniting with long lost family members. While they offer to tell you where your family roots are from, they can’t do this. It can say where your most similar DNA is found on earth.

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Fun And Trivial, Not Science

Ancestry tests are more fun and trivial than an exact science. It is fun to discuss what percentage you are of particular groups of people, but it won’t provide you much true scientific meaning. We have thousands of ancestors, and it is a very complex process to trace them.

If you find yourself in the situation that requires a paternity test, this is also done through DNA testing and comparison. Many non-invasive prenatal paternity tests can be done that are highly accurate and also very safe.

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Paternal Testing

These tests can be done after the first nine weeks of pregnancy. What are the benefits of prenatal paternity testing? These tests analyze cell-free fetal DNA, which is found in the maternal blood, which means there is no chance of misdiagnosis or incorrect results.

This technique means that testing is extremely accurate and reliable. Other tests use nucleated fetal cells, which may provide a less accurate reading. A blood sample is collected from the mother and not taken from the baby.

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A Prenatal Paternity Test Without The Risks

Other tests are invasive and pose many other risks to the mother and the child to find out the paternity. Prenatal paternity tests, however, are unable to be performed when there has been In Vitro Fertilization or if it is multiple pregnancies.

The labs using this testing will require the sample of maternal blood and then a mouth swab sample from the alleged father. The lab will then separate the blood plasma from the mother’s blood sample and locate the fetal DNA.

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How The DNA Is Tested

It will then be analyzed alongside the DNA samples from the mother and the suspected father. Using an algorithm, they will compare genetic markers between the fetal DNA and the father’s DNA. This test will then provide the answers you desire.

A result should be ready within five to seven working days, but some places offer an express testing option. It should get the results to you in three to four days. For express testing, most situations require the mother to be at least ten weeks pregnant.

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Learn More About Yourself

DNA is a fascinating thing to learn more about and try to understand its complexities. It can provide us with interesting facts about ourselves that we would have never known if we hadn’t sent off some spit in a tube.

However, these results need to be taken with a pinch of salt as some of the results are based on probability rather than actuality. There are cases when DNA testing is entirely accurate and useful, such as in family and paternal testing.

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