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Twin Zygosity Test

DNA Zygosity Test For Twins


Results In One Day!

How Can I Tell If My Twins Are “Identical” Or “Fraternal”?

This Is The Question We Hear The Most From Parents Of Twins!

Most people assume that being a twin means having a similar physical appearance. However twin type is determined long before the twins are born. The terms identical and fraternal are common words that refer to “zygosity.” Zygosity is the characteristics of the cell union that happen at conception, which results is the genetic relationship between two twins. With respect to genetic similarities or dissimilarities, twins are classified as identical or fraternal.

When one egg is fertilized by a single sperm cell and then splits, two identical, or monozygotic, twins will result. These twins are referred to as identical since the sequence of the twins’ DNA is identical. Identical twins must be of the same sex. Importantly, the term “identical” often does not apply to the actual physical or behavioral similarities between identical twins. However, identical twins tend to be very similar for traits such as hair color, hair texture, eye color, height, and weight.

When two eggs are independently fertilized by two sperm cells, fraternal or dizygotic twins result. Fraternal twins do not have identical DNA but will have half of their DNA in common, just like siblings of the same parents that are born at different times. Fraternal twins can either be of the same sex or different sex. It is interesting to note that, although there is some evidence that twinning is heritable, neither family studies nor molecular-genetic data suggest that it is either autosomal or sex-linked. 

The only 100% accurate way to determine identical or fraternal twins is by a DNA Zygosity Test.

What Is A Zygosity Test?

Since the above definition of an identical or fraternal twin refers only to the similarity or dissimilarity of the twins’ DNA, a zygosity test is a comparison of the DNA between two twins. At Journey Genetic Testing, our lab analyzes regions of DNA which are called microsatellites. These are stretches of DNA that repeat over and over again, like AACT AACT AACT AACT.

All humans have repeating stretches of DNA, and the repeats vary from one individual to another. When several of these repeat areas are the same between two siblings, it is probable they are identical twins. If the twins are different at one or more repeat markers, they are considered to be fraternal twins. Interestingly, these are almost the exact same techniques used in forensics and in paternity tests. The genes analyzed are not related to any specific physical trait such as hair color, height or personality. 

Zygosity testing works on multiples of any age, newborns to adults. The simple and non-invasive swabbing procedure allows for the rapid and painless collection of a DNA sample.

How Much Does A Twin Test Cost?

Our goal is to make our genetic testing as affordable as possible without compromising on quality. We know that some companies are advertising they offer cheap Twin Zygosity DNA test prices. We want to encourage you to be careful when considering these companies. Cheap DNA tests may have a lot of hidden or surprise costs (for example: a very high cost for more than one DNA kit, an extra charge to provide results to except by phone, etc.). A cheap DNA test usually will cost you more when everything is done, and they often don’t have the resources and trustworthiness of established DNA testing companies like ours.

We don’t offer cheap DNA services. However, we do offer very a very affordable identical twin DNA test. If fact, we have not increased the cost to our customers in over five years, even though our costs have risen along with everything else. Our affordable prices have allowed us to process thousands of DNA samples every year for lawyers, physicians, adoption agencies, and private individuals.

The cost for our DNA test to see if twins are identical or fraternal is only $109.00.

How Accurate Is Identical Twin Testing?

The only way of knowing if two or more multiples are identical is by doing a zygosity DNA test. Our twin Zygosity DNA test will determine if your twins are identical (monozygotic) or fraternal (dizygotic). The results of this test are 100% accurate, giving you a clear yes or no answer to this question.

While the testing is 100% accurate, and will give you a definite answers, that doesn’t mean that identical twins don’t share 100% of their DNA. Sound confusing? Let look at why we say this. Identical twins form from the same egg, and they get the same genetic material from both mom and dad , but that doesn’t mean they’re genetically identical by the time they’re born.

Monozygotic twins may pick up what are called genetic mutations in the womb. These mutations are nothing to be concerned about. This terms means that as their cells create and blend new strands of DNA they split into more and more cells. It is estimated that, on average, a pair of twins have genomes that differ by an average of 5.2 mutations that occur early in development. They share enough DNA to be called identical, even with the slight mutations.

The Need For Twin Zygosity Testing

Most people order a zygosity test to satisfy their curiosity, and that of their friends and family. However, there are some health conditions with where it would be useful to know if a condition experienced by one twin will be likely to be experienced by the other twin. Identical twins can donate organs to each other in certain situations. For important medical decision making, we recommend have a legal, chain of custody twin test done. Since the laboratory is AABB accredited, it just requires having an authorized DNA collector take the DNA samples, and complete a chain of custody. If you have a need for a legal document proving zygosity, please talk with one of our Genetic Consultants and we can set everything up for you.

How Long Will It Take To Get My Twin DNA Test Results?

Testing for Twin Zygosity can begin once the DNA samples arrive at the lab. If samples are being sent from more than one location, testing begins when the last sample arrives. We send you an email notification that all samples have been received, and that testing has started.

Twin Zygosity DNA test results are usually available in just 1 business days. This means if we start testing on a Monday, your results should be ready and sent to you on Tuesday, by the end of business. While uncommon, there are some circumstances that may case a slight delay in this time frame. A delay may occur if:

  • extended testing is needed to examine more genetic markers (this does not happen often);
  • you have sent something other than a mouth swab for DNA testing which requires a viability test before regular testing can begin.

Your identical twin DNA test samples are always run twice to verify the DNA profiles being reported before the results are issued. Twin Zygosity test results are reviewed, and confirmed, by a lab Ph.D., who is required to sign the results report. It is only after all of this that the report is to sent you. A report that is not reviewed, or signed, by a Ph.D. in genetics, whether for private results or a court ordered test, is something we will not provide and we would not trust those results.

The report with answer as to if your twins or triplets are identical or fraternal will be 100% accurate. We do not guarantee a specific result, only accurate ones.

Your results will be sent to the email address on your order form in a .pdf format. All reports are written in easy to understand language. If you want a permanent copy of the report, you can either print the PDF, or order a printed hard copy mailed to you.

Limitations of Zygosity Testing

There are two instances where Zygosity DNA testing has not developed to the level of accuracy we require. Because of this we are unable to perform the testing in these instances:

  • Suspected mirror image twins. Mirror image twins are identical twins that result when a fertilized egg splits later in the embryonic stage than usual, typically from day 9 to 12. Mirror image twins tend to exhibit characteristics with reversed asymmetry (e.g., one twin is left-handed and the other is right-handed). If this split happens much later than this, then the twins can be co-joined. A DNA-based zygosity test cannot determine is twins are mirror image twins. 
  • Polar body or “half-identical” twins. Polar body twins are believed to occur when the mother’s egg splits before fertilization and one half (referred to as the ‘polar body’) is also fertilized by a different sperm. This results in twins who share half their genes in common (from the mother) and the other half different (from the two sperm). They share some features of identical twins and some features of fraternal twins and are so-called half-identical twins. However, DNA-based zygosity tests are currently not available to determine if twins are polar-body twins

Benefits Of DNA Zygosity Testing Through Journey Genetic Testing

Utilizing the most advanced technology. along with standardized methods in human identity testing, our results are guaranteed to be 100% accurate. Ensuring this level of accuracy and quality control is of the utmost importance to us.

Specialization in zygosity testing allows us to offer these services at a fraction of the cost of what many testing laboratories charge. We are able to provide you access to the highest quality genetic testing services that were once out of reach because of high cost.

Our clients receive their customized DNA collection kits in one to three business days, depending on location. Once the samples are returned using the prepaid overnight FedEx mailer (USA addresses only for the return mailer), the laboratory immediately begins testing, and provides the results in just 1 business day in 99.8% of our cases. These are emailed to you the same day they are released in an PDF that is easy to read and understand.

Often Asked Questions About Twin Zygosity Testing

home twin test kit

Twin Zygosity FAQs

Approximately 30 out of every 1,000 births in the United States produce twins. One of every three sets of twins is identical.

This answer might surprise you! The answer is yes, although it is very rare. We have only seen this happen once, and it was verified by our lab Ph.D., and independent medical professionals.

Yes, fraternal twins can indeed have different fathers. One study estimated that it might occur in as many as one in 400 twin births.

Not necessarily – an inherited disease does not reflect the genetic risk to a person. Very few diseases are 100% genetic. Our environmental and lifestyle usually are the cause for most common diseases that a person may have a genetic predisposition toward. This is why identical twins do not share all diseases.

Dizygotic (fraternal) twins have been shown to be hereditary on the mother’s side, There is a greater probability of this for older mother’s and those who have undergone fertility treatments. Identical twinning does not usually run in families and is thought to happen by chance most of the time.

Males are a little more likely than females to die in the womb. And because the death rate in the womb is higher for twins than for non-twin births, female twins are more common than male twins.

Yes! Identical twins came from the same sperm and egg, so they have the same chromosomes and genes. But there are environmental differences that can affect the way they look and behave.

Our Twin Zygosity Clients Comments:

You can read more of our real customer reviews by clicking on Customer Guarantee and Reviews.

“I was always asked at the store if my twins were identical. I didn’t really know, so I did your test. The results can back so fast and know I know to tell people they are identical!” – Roxie R.
“This was the easiest thing to do. Thanks for answering all my questions before I ordered. I got the results in time for their birthday reveal. I am going to tell everyone in my Facebook group about you!” – Aspen T.
“I will admit I was skeptical because your price was a lot lower than other companies. After going though this I have to tell you I am sorry for doubting you. You did everything you said, and my results were back fast. I appreciate the value you provide for the lower cost.” – Mary W.