Lines and X Factor Chart
Sire line Sire line, classified by oldest linear grandfather
Dam line Dam line, classified by oldest linear grandmother
X Factor Chart Click [display] to display X Factor Chart
From a genetic point of view, sire lines are related to the Y chromosome and maternal lines are related to mitochondrial DNA, which both are passed on linearly. The Blood Bank also uses the terms y-position (linear sire) and m-position (linear dam).
X factor paths are lines related to the inheritance of the X chromosome (mare to son, mare to daughter, stallion to daughter but not stallion to son).