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Big Y Block Tree Introduction

The Big Y Block Tree is a vertical-block diagram of the Y-DNA Haplotree showing the relationships between you and other Big Y testers. This tool helps you visualize how the paternal lineages of you and your matches are related to each other. You will also be able to see your matches' branches and discover which and Paternal Countries of Origin have been reported for your branch and others.

Please note that Big Y test is an exploratory test that is constantly discovering previously unknown SNPs. As new SNPs are discovered and added to the Y-DNA Haplotree, this will alter the structure of the branches, and potentially move your branch further downstream. In addition, as more people test, it can help to refine SNPs currently thought to be equivalent to build an ever-increasingly accurate SNP lineage.

Accessing the Block Tree

To access from your dashboard:

  1. Sign in to your kit.
  2. On your dashboard, locate the Y-DNA Results & Tools widget.
  3. On the Y-DNA Results & Tools widget, in the Big Y section, click the Block Tree button. 

To access from your navigation bar:

  1. Sign in to your kit.
  2. On the navigation bar at the top of the page, go to Results & Tools > Big Y > Block Tree.

Block Tree Overview 

Your Branch

Your branch is located in a white block. Also, you will see Your branch displayed under the Branch Information card for your specific branch.


Branch Blocks

On the Big Y Block Tree, each branch is represented as a block. For example, the below image represents the I-A19399 branch.


In the block, the first line (e.g., I-A19399) is the primary SNP in the branch. The rest of the SNPs displayed in the block are Public Variants that are equivalent to the primary SNP.

Upstream Branch Blocks

Upstream branch blocks are the blocks that are located above a branch block.

Sibling Branch Blocks

Sibling branch blocks are the blocks located parallel or rather horizontally to the left and/or right of a branch block.

Downstream Branch Blocks

Downstream branch blocks are the blocks that are located below a branch block.

Private Variants

On the Big Y Block Tree, you will see blocks labeled Private Variants. Private Variants are one of the following;

  • mutations that are not named nor are shared between any branch members.
  • mutations that have not yet been validated and placed on the haplotree.

It is important to note that Private Variants are filtered to only include SNP calls from regions of the Y chromosome that can be reliably mapped with NGS technology. For this reason, the block tree number might be lower than what you see in your personal Big Y Private Variants list.

You can hover your cursor over a Private Variants block to see the average of Private Variants and the number of Big Y testers in that branch.


Public Variants

Public Variants are:

  • mutations that are named and are shared between branch members.
  • mutations that have been validated and placed on the haplotree. 

Branch Information

At the bottom of the page, below each branch, you will see the Branch Information card.


The Branch Information card displays the following information for the corresponding branch:

  • Countries - This section displays the number of Paternal Countries of Origin reported by participants on a branch and a flag icon for each country.
  • DNA Matches - This section displays the number of your matches that are on that branch and your matches' names.

For a more in-depth look and description of the information contained in the Branch Information card, see the Branch Information Card section in the Guide topic. 

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