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Haplotype vs. Haplogroup Edit

A haplotype is a term used to describe a haploid genotype. Essentially, it is the group of genes one will inherit from one of their parents, on either the patriarchal side or the matriarchal side of the family. These tightly connected genes belong to a group of specific alleles that reside in a distinct location on a chromosome. Haplotypes are also described as a grouping of comparable single-nucleotide polymorphisms (SNPs) found on the same chromosome. Y-chromosomal haplotypes are categorized by assignment to a letter from the alphabet with corresponding numbers (1; 2).

Europe Y-DNA

A map outlining the migration of haplogroups across Europe. SOURCE: http://en.wikipedia.org/wiki/Haplogroup_R1b_(Y-DNA)

A haplogroup is considered a group of associated haplotypes. These haplotypes are all very similar because they all contain the same SNP. These individual SNPs are what create alleles, genes, and genetic variability between beings. The content of the Y-chromosome (paternal DNA) and the mitochondrial DNA (maternal DNA) are given different haplotype designations. When a cell is undergoing meiosis, there is minute genetic shuffling between paternal DNA material and maternal DNA material; only about 5% of the Y-chromosome recombines with the X-chromosome. In the end, a son is more or less 95% genetically identical to his father (1; 2).

Y-chromosomal DNA Edit

Y-chromosomes do not come as pairs, as all other chromosomes do. This is because a male’s genetic material is made of one Y-chromosome and one X-chromosome; these respective chromosomes are each inherited from the paternal and maternal lines. In the case of X-chromosomes, a male will inherit one or the other. In the case of Y-chromosomes, a male will inherit the one Y-chromosome from his father. This inherited Y-chromosome is nearly identical to the Y-chromosome the father was born with. Very little gene shuffling occurs within the Y-chromosome itself, so it remains almost indistinguishable when it is passed along (95% similar). Save a few random mutations, a son and father should contain half of the same genetic material (2).

SNPs are also known as Unique-event polymorphisms (UEPs); these represent haplogroups. Short tandem repeats (STRs) represent haplotypes. Essentially, the STRs comprise the SNPs to create a mostly unique haplogroup (2).

Y-chromosome haplogroups

An evolutionary tree of Y chromosome haplogroups. SOURCE: http://en.wikipedia.org/wiki/Haplogroup

Y-chromosomal DNA can be divided into two categories: the SNPs and the STRs (2).

SNPs and STRs Edit

Single-nucleotide polymorphisms Edit

The UEP and SNP material represents a linear inheritance of events that have only happened once in history, i.e. conception between two individuals with unique DNA content. One can then be genetically traced back to a place within the family tree of human history using these UEPs (2).

Short tandem repeats Edit

The STR material represents more recent genealogy and genetic changes. This is because Y-chromosome STRs mutate more easily than SNPs, and therefore are representative of more recent evolution and history. It has been shown that these Y-STR events are not necessarily unique to individuals or families; different and totally unassociated events and histories tend to overlap in the content of their STRs (2).  

Haplogroup R1b1b2a1a Edit

Haplogroups have been used to trace back the history of human evolution and migration globally, as certain haplogroups are associated with distinct geographical regions. For example, haplogroup R1b is a haplogroup of specifically Y-chromosomal DNA. R1b is considered the most dominant paternal lineage of all Western Europe. R1b is also designated R-M343; this means R1b is the result of an SNP mutation at the M343 site on the Y-chromosome. R1, the parent haplogroup of R1b, is estimated to be 18,500 years old (3).  

Haplogroup R

A tree outlining the history of the R1b1b2a1a haplogroup. SOURCE: http://www.roperld.com/R1b1b2a1aYHaplogroupCharts.pdf

According to John Burke’s individual profile on the 23andMe website, he is within the haplogroup R1b1b2a1a. This haplogroup is a subgroup of R1b1b2, a more broad haplogroup. John Burke’s haplogroup has been traced to the Basque area between France and Spain. His individual group is nearly 17,000 years old. Malcolm Gladwell, a Canadian author, shares the same haplogroup as John Burke (4).

References Edit

1) Haplogroup. Wikipedia. http://en.wikipedia.org/wiki/Haplogroup. Updated August 30, 2014. Accessed September 12, 2014.

2) Haplotype. Wikipedia. http://en.wikipedia.org/wiki/Haplotype. Updated August 4, 2014. Accessed September 12, 2014.

3) Haplogroup R1b (Y-DNA). Wikipedia. http://en.wikipedia.org/wiki/Haplogroup_R1b_(Y-DNA). Updated September 4, 2014. Accessed September 12, 2014.

4) Paternal Line. 23andMe. https://www.23andme.com/you/haplogroup/paternal/. Updated 2014. Accessed September 12, 2014.