Unique event polymorphism / UEP - in DNA genealogy, means a genetic marker corresponding to one extremely rare mutation . It is believed that all carriers of such a mutation inherit it from one ancestor, and therefore all cases of the discovery of this mutation throughout the globe are the result of one mutational event.
The discovery and extensive testing of new unique event polymorphisms is a key tool for a detailed analysis of the paternal and maternal ancestry and the creation of hereditary DNA trees of the Y chromosome and haplogroups of mitochondrial DNA .
Mutations that are classified as unique event polymorphisms are typically single nucleotide polymorphisms — replacing one base with another in a DNA sequence, so the terms “unique event polymorphism” and “single nucleotide polymorphism” are often used interchangeably. Polymorphisms of unique events can also be large-scale, for example, YAP insertion, which determines haplogroups of Y-DNA D and E , or deletion of sites.
Short Tandem Repeat Comparison (STRs)
Polymorphisms of unique events can be contrasted with short tandem repeats (STRs), another type of genetic variation used in DNA genealogy.
Unlike unique event polymorphisms, short tandem repeat (STR) sequences have high variability , and therefore there is a high probability that in just a few generations one set of such repeats can be replaced by another set with an increased number of repeats. This makes individual haplotypes of short tandem repeats more specific for individual groups of people. However, this also means, at least for markers of short tandem repeats of the Y chromosome, that completely unrelated pedigrees can have similar combinations of markers of short tandem repeats on the Y chromosome in an independent manner.
In a number of rare cases of large deletions causing sudden large changes in the number of STR repeats in the Y chromosome, Y-STR markers can acquire the status of markers of polymorphisms of unique events. Such cases differ from the increase or decrease in the number of repetitions in different pedigrees. For example, such changes in DYS 413 distinguish haplogroups J2a1 and J2a in the haplogroup of DNA of the Y chromosome J.
See also
- Haplogroup
- Short tandem repeat
- Single nucleotide polymorphism