In 2006 the International Society of Genetic Genealogy (ISOGG) listed 22 variants on the R1b section of their Y Tree. In 2011 R1b-DF21 was added to the ISOGG’s Y Tree, and today there are 58 verified SNPs under DF21. Moreover there are hundreds of variants that have been identified in DF21 men that need additional research and testing in order to meet the ISOGG listing criteria for SNP Inclusion. This website will be developed to keep track of these newly discovered SNPs, and to direct people to resources. It is a work in progress and is being done on a volunteer basis.
"The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences."1
"Single nucleotide polymorphisms, frequently called SNPs (pronounced “snips”), are the most common type of genetic variation among people. Each SNP represents a difference in a single DNA building block, called a nucleotide. For example, a SNP may replace the nucleotide cytosine (C) with the nucleotide thymine (T) in a certain stretch of DNA."1
The R1b-DF21 haplogroup “is a genetic population group of people who share a common ancestor on the patrilineal...line"2. It is defined by a C to T mutation on the Y chromosome at position 9878915. DF21/S192 (i.e. also known as S192), is on the Y Tree below CTS241/DF13/S521 which is itself below L21/M529/S145 which is in turn below P312/PF6547/S116. At this time DF21 has five officially recognized subclades; FGC3213, FGC3903/S5201/Y2890, S5488, S5456, and S971/Z3017. There are also several DF21 clade members who do not appear to be a member of any of these subclades. These men will be identified as DF21* until a new subclade is correctly placed on the ISOGG tree.
The debate about the age of DF21 is in ongoing. Recently the researchers at Y Full posted on their website that they estimate the time to most recent common ancestor (TMRCA) was 4100 ybp. That is a thousand years older than any time frame I had previously heard mentioned. This new research is possible because the rapid and steep decrease in the price of next generation sequencing (NGS). Still a relatively small number of men have taken one of the tests necessary to identify their genetic variants. And because the vital data is not yet available the age of DF21 will probably be debated for many more years.