Test to distinguish in-paralogs and out-paralogs. A What is the relationship of sequences y1 and y2 with regard to x? Identify which branch to place the root by finding an out-group sequence z. B If the root on the branch leading to x, then y1 and y2 are out-paralogs. C If duplication takes place after speciation, y1 and y2 are in-paralogs. D To test if y1 and y2 are in-paralogs, we confirm that the distance d of the internal branch is greater than zero.