Identical twins are genetically different

Identical twins may not be so identical after all!
Although identical twins supposedly share all of their DNA, they acquire several genetic changes early in development that could set them on different paths, scientists say.
These genetic differences between 'identical' monozygotic twins have now been discovered by the scientists.
So far there have been only theoretical considerations against the experimental finding and dogma that monozygotic twins are genetically fully identical. Statistically, around 6 of 1,000 males are identical twins, researchers said.
A multidisciplinary Eurofins team in the Eurofins flagship Genomics laboratory in Ebersberg, Germany, has successfully completed a research project to genetically discriminate "identical" monozygotic twins.

Up to now, forensic DNA fingerprinting testing could not be used in crime or paternity cases involving identical twins, as there was no possibility of genetically discriminating between them.

Eurofins scientists applied ultra-deep next generation sequencing and associated bio-informatics techniques.
They sequenced DNA from sperm samples of two twins and from a blood sample of the child of one twin. Bio-informatics analysis revealed five mutations, so called Single Nucleotide Polymorphisms (SNPs) present in the twin father and the child, but not in the twin uncle.
The SNPs were confirmed by classical Sanger sequencing. The results give experimental evidence for the hypothesis that rare mutations will occur early after or before the human blastocyst has split into two, the origin of twins, and that such mutations will be carried on into somatic tissue and the germ line.

The genetic differences found and the method used provide a solution to solve forensic and paternity cases involving monozygotic twins as originator of DNA traces in crime, or as alleged fathers. Eurofins is the first to offer such a test.
"Eurofins scientists are the first to prove that monozygotic twins are genetically not absolutely identical. As the only provider worldwide Eurofins can now offer DNA forensic and paternity testing to discriminate identical twins to authorities, courts and individuals," Bruno Poddevin, Senior Vice-President of the Genomic Services division and head of the Forensics laboratory at Eurofins, said.
The study was published in the journal Forensic Science International: Genetics.