Haplotype
A haplotype (haploid genotype) is a group of alleles in an organism that are inherited together from a single parent.
Each clade under a branch, containing haplotypes with a single shared ancestor, is called a haplogroup.
These methods work by applying the observation that certain haplotypes are common in certain genomic regions.
In genetics, a gametic phase represents the original allelic combinations that a diploid individual inherits from both parents.
A human male should largely share the same Y chromosome as his father, give or take a few mutations; thus Y chromosomes tend to pass largely intact from father to son, with a small but accumulating number of mutations that can serve to differentiate male lineages.
The UEP results represent the inheritance of events it is believed can be assumed to have happened only once in all human history.
These can be used to identify the individual's Y-DNA haplogroup, his place in the "family tree" of the whole of humanity.
Different Y-DNA haplogroups identify genetic populations that are often distinctly associated with particular geographic regions; their appearance in more recent populations located in different regions represents the migrations tens of thousands of years ago of the direct patrilineal ancestors of current individuals.
Instead, the clusters of Y-STR haplotype results inherited from different events and different histories tend to overlap.
These results will tend to significantly overlap the (similarly broad) clusters of Y-STR haplotypes associated with other haplogroups.
This makes it impossible for researchers to predict with absolute certainty to which Y-DNA haplogroup a Y-STR haplotype would point.
If the UEPs are not tested, the Y-STRs may be used only to predict probabilities for haplogroup ancestry, but not certainties.
A cluster of similar Y-STR haplotypes may indicate a shared common ancestor, with an identifiable modal haplotype, but only if the cluster is sufficiently distinct from what may have happened by chance from different individuals who historically adopted the same name independently.
Commercial DNA-testing companies now offer their customers testing of more numerous sets of markers to improve definition of their genetic ancestry.
This is more than establishing that a randomly selected member of the population is unlikely to have such a close match by accident.
Because of the difficulty, establishing relatedness between different surnames as in such a scenario is likely to be impossible, except in special cases where there is specific information to drastically limit the size of the population of candidates under consideration.
The term "haplotype" was first introduced by MHC biologist Ruggero Ceppellini during the Third International Histocompatibility Workshop to substitute "pheno-group".
