///Y-DNA Trees and How They Grow

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Y-DNA Trees and How They Grow

We just covered how the Y Chromosome Consortium formed and in 2002 published a united tree for the paternal Y-chromosome tree. The other thing they outlined in their 2002 paper was the ways the tree can change over time. Today's post will go over these.

First though, let's review vocabulary.

Binary polymorphism – A genetic change with two possible states. That is positive or negative — derived or ancestral. Most binary polymorphisms on the 2017 tree are Y-SNPs. For simplicity, I usually refer to all types of binary polymorphisms as variants.
Haplogroup – A branch on the Y-chromosome Tree defined by one or more binary polymorphism.
Y-SNP – A single nucleotide polymorphism. This is a genetic change of exactly one base pair to another value, A changes to C. This is a type of binary polymorphism.
Y-chromosome – The human male sex chromosome. It is passed from a father to his sons each generation with only small random changes.

Now, there are three types of changes to the Y-chromosome:

  1. New Variant Join – A new binary polymorphism, variant, joins two branches. This is now less common with Big Y type tests, but it can still happen if the new binary polymorphism is not in an area covered by Big Y.
  2. New Variant Split – A new binary polymorphism, variant, splits two branches. This is the most common type of change we have with Big Y type tests.
  3. New Sample Split – A new sample splits an old haplogroup, branch. This is the second most common type of change with Big Y type tests.

Example Tree – This is the base tree before each type of potential change. I am using the tree from the 2002 paper. The H and G trees no longer look like this.

Tree Haplogroup Nomenclature
  by Lineage by Mutation
  G   M102 G G-M201*
    1   P20 G1 G-P20
    2   P15 G2 G-P15*
      a   P16 G2a G-P16*
        1   P17 P18 G2a1 G-P17 or G-P18
  H   M52 M69 H H-M52* or H-M69*
    1   M82 H1 H-M82*
      a   M36 H1a H-M36
      b   M97 H1b H-M97
      c   M39 M138 H1c H-M39 or H-M138


New Variant Join
– This shows what would happen if a new variant were found that joined the H-M36 and H-M97 haplogroups under H-M82 but not the H-M39 branch.

Tree Haplogroup Nomenclature
  by Lineage by Mutation
  G   M102 G G-M201*
    1   P20 G1 G-P20
    2   P15 G2 G-P15*
      a   P16 G2a G-P16*
        1   P17 P18 G2a1 G-P17 or G-P18
  H   M52 M69 H H-M52* or H-M69*
    1   M82 H1 H-M82*
      a New H1a H-New
        1   M36 H1a1 H-M36
        2   M97 H1a2 H-M97
      b   M39 M138 H1b H-M39 or H-M138


New Variant Split
– This is when a new variant is found that splits a lineage. In this example, a new variant is found in some men who have M36 but not all of them. This creates a new branch, haplogroup, under H-M36.

Tree Haplogroup Nomenclature
  by Lineage by Mutation
  G   M102 G G-M201*
    1   P20 G1 G-P20
    2   P15 G2 G-P15*
      a   P16 G2a G-P16*
        1   P17 P18 G2a1 G-P17 or G-P18
  H   M52 M69 H H-M52* or H-M69*
    1   M82 H1 H-M82*
      a M36 H1a H-M36
        1   New H1a1 H-New
      b   M97 H1b H-M97
      c   M39 M138 H1c H-M39 or H-M138


New Sample Split
– This is where a new sample is positive for some but not all of the variants on a branch. In the example below, a new person tests who has M52 but not M69. H-M69 then becomes its own branch, haplogroup, under H-M52

Tree Haplogroup Nomenclature
  by Lineage by Mutation
  G   M102 G G-M201*
    1   P20 G1 G-P20
    2   P15 G2 G-P15*
      a   P16 G2a G-P16*
        1   P17 P18 G2a1 G-P17 or G-P18
  H   M52 H H-M52*
    1 M69 H1 H-M69*
      a   M82 H1a H-M82*
        1   M36 H1a1 H-M36
        2   M97 H1a2 H-M97
        3   M39 M138 H1a3 H-M39 or H-M138

2018-01-18T16:37:09+00:00 December 29th, 2017|Categories: News|Tags: , , , , , |