Wednesday, June 9, 2010

Y-DNA Testing

Y-DNA refers to the DNA found on the Y Chromosome. It is contained in the cell nucleus of all males. All healthy humans inherit 23 Chromosome Pairs from their parents. The last two are the sex chromosomes, or the X and Y. Only males inherit the Y chromosome, so it can only be used to trace the direct paternal line. Simply speaking, a man inherits his Y chromosome from his father who inherited it from his father who inherited it from his father and so on. Testing of this Y-DNA can reveal the ancient origins of a person's direct paternal line. It can also be of great genealogical value since the Y-DNA traditionally follows the same inheritance pattern as surnames. As the surname is passed down from male to male, so is the Y-DNA. Used in conjunction, a male can often identify which ancestral line he belongs to by matching with others of the same or similar surnames. Though not guaranteed, an adoptee may even find success in discovering his biological surname by testing his Y-DNA. Some testees have not yet found success with this type of testing due to the lack of matches in the databases. However, time should rectify this problem for most with the growing popularity of DNA testing. For cultures that did not utilize surnames in the traditional way until the 20th Century, such as Scandinavia, the Y-DNA can still be useful in identifying probable origins and migration patterns.
Upon testing your Y-DNA you will receive a list of the short tandem repeats (STRs) contained on your Y chromosome that determines your haplotype. You may also be assigned a haplogroup based on single-nucleotide polymorphisms (SNPs) contained in your Y-DNA. Matches are measured by genetic distance (GD) and can estimate the time to the most recent common ancestor (TMRCA) for two males depending on how closely their individual haplotypes match each other.
Y-DNA testing currently available includes both SNP and STR testing. For STRs, a male may order anywhere from 12 markers to over 100 markers. The industry standard is generally 37 or 67 markers at this time. Individual SNPs or panels of SNPs can be ordered to determine and refine one's haplogroup. Scientists and hobbyists are continually discovering new SNPs, this further refining the Y Haplogroups.
For further clarification on the Y Chromosome (for beginners) go to Sorenson's Animations here.

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