Thursday, January 4, 2018

Your DNA Truth

Background

The Y chromosome is passed down directly from father to son; all male humans (Y chromosomes) today trace back to a single prehistoric father termed "Y-chromosomal Adam" originating in Africa.[21] The Y chromosome spans about 60 million base pairs (the building blocks of DNA) and represents about 2 percent of the total DNA in all human cells.[22] The original "Y chromosomal Adam"-DNA sequencing has mutated rarely over the 20,000 generations, but each time a new mutation occurs, there is a new branch in a haplogroup, resulting in a new subclade (single-nucleotide polymorphism (SNP)).[23]

Both females and males inherit their Mitochondrial DNA (mtDNA) from only their mother.[24] MtDNA mutations are also passed down relatively unchanged from generation to generation, so all humans share the same mtDNA-types. The logical extension of this is that all humans ultimately trace back to one woman, who is commonly referred to as Mitochondrial Eve.[25][26] This line of biological inheritance, therefore, stops with each male.[27] Consequently, Y-DNA is more commonly used by the general public for tracing genetic heritage of a direct male line.[27][28][29]

An autosome (atDNA) is a chromosome that is not a sex chromosome – that is to say, there are an equal number of copies of the chromosome in males and females.[2] Autosomal DNA testing is generally used to determine the "genetic percentages" of a person's ancestry from particular continents/regions or to identify the countries and "tribes" of origin on an overall basis. Genetic admixture tests arrive at these percentages by examining locations (SNPs) on the DNA where one nucleotide has "mutated" or "switched" to a different nucleotide.[2] One way to examine the support for particular colonization routes within the American landmass is to determine whether a closer relationship between zygosity and geography is observed when "effective" geographic distances are computed along these routes, rather than along shortest-distance paths

Y-DNA

The Y chromosome consortium has established a system of defining Y-DNA haplogroups by letters A through to T, with further subdivisions using numbers and lower-case letters

Haplogroup Q
Q-M242 (mutational name) is the defining (SNP) of Haplogroup Q (Y-DNA) (phylogenetic name). Within the Q clade, there are 14 haplogroups marked by 17 SNPs.2009[32][33] In Eurasia, haplogroup Q is found among indigenous Siberian populations, such as the modern Chukchi and Koryak peoples. In particular, two groups exhibit large concentrations of the Q-M242 mutation, the Ket (93.8%) and the Selkup (66.4%) peoples.[34] The Ket are thought to be the only survivors of ancient wanderers living in Siberia.[35] Their population size is very small; there are fewer than 1,500 Ket in Russia.2002[35] The Selkup have a slightly larger population size than the Ket, with approximately 4,250 individuals.[36]

Starting the Paleo-Indians period, a migration to the Americas across the Bering Strait (Beringia) by a small population carrying the Q-M242 mutation took place.[10] A member of this initial population underwent a mutation, which defines its descendant population, known by the Q-M3 (SNP) mutation.[37] These descendants migrated all over the Americas.[32]

Haplogroup Q-M3 is defined by the presence of the rs3894 (M3) (SNP).[3][35][38] The Q-M3 mutation is roughly 15,000 years old as that is when the initial migration of Paleo-Indians into the Americas occurred.[39][40] Q-M3 is the predominant haplotype in the Americas, at a rate of 83% in South American populations,[8] 50% in the Na-Dené populations, and in North American Eskimo-Aleut populations at about 46%.[34] With minimal back-migration of Q-M3 in Eurasia, the mutation likely evolved in east-Beringia, or more specifically the Seward Peninsula or western Alaskan interior. The Beringia land mass began submerging, cutting off land routes
Since the discovery of Q-M3, several subclades of M3-bearing populations have been discovered. An example is in South America, where some populations have a high prevalence of (SNP) M19 which defines subclade Q-M19.[8] M19 has been detected in (59%) of Amazonian Ticuna men and in (10%) of Wayuu men.[8] Subclade M19 appears to be unique to South American Indigenous peoples, arising 5,000 to 10,000 years ago.[8] This suggests that population isolation and perhaps even the establishment of tribal groups began soon after migration into the South American areas.[35][43] Other American subclades include Q-L54, Q-Z780, Q-MEH2, Q-SA01, and Q-M346 lineages. In Canada, two other lineages have been found. These are Q-P89.1 and Q-NWT01.

The principal-component analysis suggests a close genetic relatedness between some North American Amerindians (the Chipewyan and the Cheyenne) and certain populations of central/southern Siberia (particularly the Kets, Yakuts, Selkups, and Altays), at the resolution of major Y-chromosome haplogroups.[8] This pattern agrees with the distribution of mtDNA haplogroup X, which is found in North America, is absent from eastern Siberia, but is present in the Altais of southern central Siberia. Similarly, the Asian populations closest to Native Americans are characterized by a predominance of lineage P-M45* and low frequencies of C-RPS4Y