written by: Sonal Panse•edited by: Leigh A. Zaykoski•updated: 1/31/2010
Passed down through the paternal line, the Y chromosome haplogroup T DNA was considered unique to people of Arab and African descent. It has also been found, however, in European and American men. The spread of Islam or trading in ancient times may explain this.
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If you're a male belonging to the Y chromosome haplogroup T, you probably can trace your ancestral roots back to Mesopotamia. It's interesting how DNA findings have helped confirm or trace human historical migrations.
Let's start with the basics. Each of our cells contains 23 pairs of chromosomes, that is, 44 chromosomes in all. These include 22 pairs of autosomal chromosomes, which carry diverse genetic information about the individual, and one pair of sex chromosomes, which determine the sex of the person. The two sex chromosomes are the X-chromosome and the Y-chromosome. Females carry two X-chromosomes, and males carry one X-chromosome and one Y-chromosome. The Y-chromosome, which we are interested in in this article, is passed down the male line. Except for small genetic variations over the generations, it more or less remains the same. This means that it is possible for researchers to trace the paternal ancestry by studying the Y-chromosome and regarding the genetic variations as markers in the different paternal relationships. Since different populations from different areas have different Y-chromosome genetic variations, researchers are able to identify the geographical location from where a person originated.
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Haplotypes and Haplogroups
An haplotype, also known as haploid genotype, is a set of similar and closely associated genetic variations that are found on the same chromosome. The variations or mutations on the Y-chromosome, like the single nucleotide polymorphisms (SNPs), are what researchers find useful in determining ancestry. An haplogroup, of course, is a group of these haplotypes.
To make the definition of haplogroups easier, the Y chromosome consortium has divided haplogroups with capital alphabet letters from A to T, further sub-divisions being made with lower case letters and numbers.
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Haplogroup T was formerly, between 2002-2008, known as Haplogroup K2. Researchers believe that this haplogroup originated in Mesopotomia some 10,000 years ago and then spread elsewhere either with the spread of Islam or with the increased trading contacts between the Mesopotamians and other cultures. This theory might explain why a good percentage of men from the region - Iraq, Egypt, Qatar, UAE, Lebanon and Oman - have haplogroup T DNA, and why this DNA has also been found, in smaller percentages, amongst the Fulani people of West Africa, amongst the people from the eastern Baltic region, and amongst people from the Andalusia and Cantabria regions in Spain. A small percentage of men from Germany, France, Portugal and the UK have also been found to belong to this group, but the highest percentage of haplotype T men in Europe come from Italy.
Two well-known members of Y chromosome haplogroup T are Czar Nicholas II of Russia and the American President Thomas Jefferson.