Science News – December 12, 2013

In a recent breakthrough in genetic research, Eurofins Scientific, a European leader in genetic testing, developed a testing method to

distinguish the DNA of identical twins

.

 

While there have been theories on how to differentiate monozygotic twins — or twins that result from one zygote splitting into two embryos that share the same DNA —criminal and paternity casework has been unable to resolve this issue. Around 6 out of 1,000 males are identical twins, leading to complications in real-world criminal cases

as seen in Colorado

,

France

and the United Kingdom.

 

The structure of DNA is comprised of four base pairs — or building blocks — that repeat in various ways. The differences between specific lengths of DNA

form the basis for standard forensic DNA testing

. While identical twins have the same sequence in the portions of DNA used in forensic testing, Eurofins examined if other DNA differences exist.

 

Eurofins sequenced samples of DNA from twins and their offspring and found that certain Single Nucleotide Polymorphisms (SNPs), which are individual mutations that occur only at one base pair in the DNA, were present. Researchers found several SNPs differences between the twins, but discovered that the mutations were passed down to their respective offspring. Therefore, the specific mutations could only have occurred after the zygote split, causing any single changes in DNA to be unique to a specific twin.

 

Determining where SNP mutations commonly occur in twins enabled Eurofins to create a method for discriminating between the DNA of identical twins. While this methodology has not been validated for coursework, this research is a promising first step in overcoming the challenge of identical twins in criminal and paternity cases.