Updates to the Y Chromosome Tree

At last weekend’s Family Tree DNA 5th International Conference on Genetic Genealogy for Project Administrators, Michael Hammer, PhD presented an update on the Y chromosome tree.

Michael Hammer PhD

Michael Hammer, PhD

SOURCE: Michael Hammer, PhD (Houston, Harris County, Texas). Photographed by Stephen J. Danko on 15 March 2009.

Over 600 single nucleotide polymorphisms (SNPs) on the Y chromosome have been mapped in 20 major haplogroups (A-T). The SNPs mapped last year were mostly in haplogroup R.

New discoveries include:

  • 2 new SNPs in haplogroup E;
  • 7 new mutations (including 1 new defining mutation) for a total of 18 total mutations and 2 new subclades in haplogroup H;
  • 5 new mutations for a total of 34 mutations and 2 new subclades in haplogoup I;
  • 4 new mutations in haplogroup J2, 2 new subclades and 43 mutations total in haplogroup J;
  • 1 new mutation for a total of 11 mutations in haplogroup N;
  • 12 new mutations for a total of 54 mutations, and 9 new subclades in haplogroup R;
  • No new mutations yet in haplogroups S and T;
  • 9 new mutations and 7 new subclades are coming up.

With the large number of new mutations discovered in haplogroup R, Dr. Hammer presented a schematic showing the divergence of haplogroup R.

  • Mutation M269+ (R1b1b2) entered Europe.
  • Mutation P311+ (U106+) (R1b1b2a1a) split to Poland.
  • Mutation U152+ (R1b1b2a1b2) split to Czechoslovakia.
  • Mutation SRY2627+ (R1b1b2a1b3) split to the Iberian Peninsula.
  • Mutation L21+ (R1b1b2a1b5) split to Britain, especially Ireland, Scotland, and Wales.

Interestingly, Dr. Hammer stated that this entire group, R1b1b2 is difficult to predict from short tandem repeats (STRs), even at 67 markers. Deep clade testing using SNPs is necessary for this group.

Finally, Dr. Hammer discussed the pigmentation locus SLC24A5, which mutated only once. A single SNP explains 25-38% of pigmentation in Europeans. This mutation became fixed about 10,000 years ago, but the selective process began 20,000 years ago. The SLC24A5 pigmentation SNP may have expanded out of the last glacial maximum refugia during the fixation process.

Copyright © 2009 by Stephen J. Danko

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