genetic genealogy Genetic genealogy is the use of genealogical DNA tests, i.e., DNA profiling and DNA testing, in combination with traditional genealogical methods, to infer genetic relationships between individuals. This application of genetics came to be used ...

, a unique-event polymorphism (UEP) is a

genetic marker A genetic marker is a gene or DNA sequence with a known location on a chromosome that can be used to identify individuals or species. It can be described as a variation (which may arise due to mutation or alteration in the genomic loci) that can be ...

that corresponds to a mutation that is likely to occur so infrequently that it is believed overwhelmingly probable that all the individuals who share the marker, worldwide, will have inherited it from the same common ancestor, and the same single mutation event. Generally, UEP is an

allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chrom ...

for which all copies derive from a single

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, m ...

al event. In genetic genealogy, the

mutations In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, m ...

considered to be UEPs can be any

germline mutation A germline mutation, or germinal mutation, is any detectable variation within germ cells (cells that, when fully developed, become sperm and ova). Mutations in these cells are the only mutations that can be passed on to offspring, when either a m ...

. They are usually

single-nucleotide polymorphism In genetics, a single-nucleotide polymorphism (SNP ; plural SNPs ) is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in a sufficiently ...

s (SNP) – the replacement of one letter by another in the DNA sequence, and the terms UEP and SNP are often loosely used interchangeably. But UEPs may also be large-scale additions, such as the

YAP Yap ( yap, Waqaab) traditionally refers to an island group located in the Caroline Islands of the western Pacific Ocean, a part of Yap State. The name "Yap" in recent years has come to also refer to the state within the Federated States of Micr ...

insertion that defines Y-DNA haplogroup DE, inversions or deletions. The discovery and widespread testing of new UEPs has been the key to the increasingly detailed analysis of the

patrilineal Patrilineality, also known as the male line, the spear side or agnatic kinship, is a common kinship system in which an individual's family membership derives from and is recorded through their father's lineage. It generally involves the inheritan ...

and

matrilineal Matrilineality is the tracing of kinship through the female line. It may also correlate with a social system in which each person is identified with their matriline – their mother's lineage – and which can involve the inheritance ...

ancestry of mankind into more distinct family trees of

Y-DNA The Y chromosome is one of two sex chromosomes (allosomes) in therian mammals, including humans, and many other animals. The other is the X chromosome. Y is normally the sex-determining chromosome in many species, since it is the presence or abse ...

and

mtDNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial DNA ...

haplogroup A haplotype is a group of alleles in an organism that are inherited together from a single parent, and a haplogroup (haploid from the el, ἁπλοῦς, ''haploûs'', "onefold, simple" and en, group) is a group of similar haplotypes that share ...

s. UEPs in X and

autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosom ...

chromosomes are also used to trace genealogy, to extend the time ranges available for Y-DNA and mtDNA.

Comparison with short tandem repeats (STRs)

The properties of UEPs can be contrasted with those of

short tandem repeat A microsatellite is a tract of repetitive DNA in which certain DNA motifs (ranging in length from one to six or more base pairs) are repeated, typically 5–50 times. Microsatellites occur at thousands of locations within an organism's genome. ...

sequences (STRs), the other main type of genetic variation used in

genealogical DNA test A genealogical DNA test is a DNA-based test used in genetic genealogy that looks at specific locations of a person's genome in order to find or verify ancestral genealogical relationships, or (with lower reliability) to estimate the ethnic mixt ...

ing. Unlike UEPs, STR sequences are highly variable. There is a significant probability that one of a set may have changed its repeat number after only a few generations. That makes a particular STR

haplotype A haplotype ( haploid genotype) is a group of alleles in an organism that are inherited together from a single parent. Many organisms contain genetic material ( DNA) which is inherited from two parents. Normally these organisms have their DNA o ...

much more specific, matching a much smaller number of people. But, it also means that, at least in the case of

Y-STR A Y-STR is a short tandem repeat (STR) on the Y-chromosome. Y-STRs are often used in forensics, paternity, and genealogical DNA testing. Y-STRs are taken specifically from the male Y chromosome. These Y-STRs provide a weaker analysis than autoso ...

markers, quite unrelated lineages may have converged to the same combination of Y-STR markers entirely independently by different routes. Matching Y-STR markers by themselves cannot be used to indicate genetic relatedness. The exception is those few cases where Y-STR markers can take on the status of UEPs. This is the case of the occurrence of a large-scale deletion event, which caused a sudden big change in the Y-STR repeat number, rather than the usual single increment or decrement. Such an occurrence can be considered to have been a unique one-off in a group of lineages. Such a change in the

DYS413, for example, distinguishes subgroup J2a1 from J2a in Y-DNA haplogroup J.

References

{{Reflist

External links

* ISOG
Y-DNA Tree Index
Genetic genealogy

Comparison with short tandem repeats (STRs)

See also

References

External links