Identical twins present exactly the same DNA profile as each other, and this has created legal conundrums when it was not possible to tell which of the pair was guilty or innocent of a crime. This has led to prosecutions being dropped, rather than run the risk of convicting the wrong twin.
Now Dr. Graham Williams and his Forensic Genetics Research Group at the University of Huddersfield have developed a solution to the problem and published their findings in the journal Analytical Biochemistry.
It is based on the concept of DNA methylation, which is effectively the molecular mechanism that turns various genes on and off.
As twins get older, the degree of difference between them grows as they are subjected to increasingly different environments. For example, one might take up smoking, or one might have a job outdoors and the other a desk job. This will cause changes in the methylation status of the DNA.
“What HRMA does is to subject the DNA to increasingly high temperatures until the hydrogen bonds break, known as the melting temperature. The more hydrogen bonds that are present in the DNA, the higher the temperature required to melt them,” explains Dr Williams.
“Consequently, if one DNA sequence is more methylated than the other, then the melting temperatures of the two samples will differ — a difference that can be measured, and which will establish the difference between two identical twins.”
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