Are identical twins not identical?

A new study is forcing scientists to refine their thinking on the genetics of twins.

We know that identical twins are formed from a single fertilized egg, which goes on to split into separate embryos. This means that the twins’ DNA is exactly the same and they are known as monozygotic.

However, after sequencing the DNA from 387 pairs of identical twins, scientists in Iceland have found ‘early mutations’ that separate identical twins.

A mutation occurs when a cell divides and an error is made while the DNA is being duplicated. Such a mutation can affect physical features, for example, it could make one twin taller than the other. It can also affect susceptibility to certain diseases, possibly putting one sibling at greater risk of some cancers. On average, the researchers found that identical twins have 5.2 mutations, but some pairs have up to 100.

In fact, geneticist Kári Stefánsson from the University of Iceland, said that his team found a mutation present in all cells of the body of one twin, but none in the other twin at all.

In the past, it was believed that physical differences between twins may have been the result of environmental factors, including nutrition and lifestyle. This new research published in the journal Nature Genetics [1], will force scientists to rethink the influences of genetics and environment.

Order a Twin Zygosity DNA Test Online

How do you know if your twin is identical?

Twins will be identical or fraternal depending on how the babies were formed. The only way to know for sure whether twins are identical or fraternal is through DNA twin testing (also known as zygosity testing).

Identical vs fraternal twins

The twin test involves analyzing tiny amounts of DNA from inside each twin’s mouth. A simple mouth swab is all that is needed to collect these samples. When these samples are returned to our laboratory for testing, our DNA scientists examine specific markers present in repeat sections of DNA and compare these between the tested individuals. Identical twins will share the same DNA profile whereas non-identical siblings will have different DNA profiles. Mutations as reported in the Icelandic study will not affect these results.

AlphaBiolabs’ Twin testing costs just $119 online with results and a keepsake certificate in 3–5 days. An increasing and novel use of a twin test is to use the DNA profile to create a unique gift for new parents, their children, and friends and family. The DNA profile can also be made into exclusive artwork.

To order your test or for more information on Twin testing, please contact us via Live Chat, email info@alphabiolabsusa.com or call now at 727-325-2902.

[1] Differences between germline genomes of monozygotic twins.https://doi.org/10.1038/s41588-020-00755-1