NCJ Number
245531
Journal
Forensic Science International: Genetics Volume: 9 Dated: March 2014 Pages: 42-46
Date Published
March 2014
Length
5 pages
Annotation
This report describes how the identification of extremely rare mutation though ultra-deep next-generation sequencing can distinguish between monozygotic (MZ) twins, who are considered genetically identical.
Abstract
The findings show that the described method for distinguishing MZ twins is not only applicable to paternity cases, but also to forensic cases with ectodermal traces such as contact stains, skin scales, hair, buccal mucosa, or semen stains found at crime scenes; it is also likely to work with blood stains. The analytical methodology also enables the re-analysis of "cold" cases of sufficient relevance and approaching new cases that involve MZ twins as donors of stain material. The study sequenced DNA from sperm samples of two twins and from a blood sample of the child of one twin. Bioinformatics analysis revealed five 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 findings provide empirical evidence for the hypothesis that rare mutations will occur early after the human blastocyst has split into two, the origin of twins, and that such mutations will be carried on into somatic tissue and the germline. Mutations that can be used to identify a specific twin must have occurred after separation of the morula, or early before separation with exclusive presence in the cells belonging later to only one of the twins. Generally, only mutations present in the germline are inheritable. Mutation events that occur later in the somatic lineages will not be transmitted to any potential offspring. 1 table and 3 figures