Y linkage, also known as holandric inheritance (from Ancient Greek ὅλος hólos, "whole" + ἀνδρός andrós, "male"), describes traits that are produced by genes located on the Y chromosome. It is a form of sex linkage.
Y linkage can be difficult to detect. This is partly because the Y chromosome is small and contains fewer genes than the autosomal chromosomes or the X chromosome. It is estimated to contain about 200 genes. It was once believed that the human Y chromosome was thought to have little importance. While the Y-chromosome is sex-determining in humans and some other species, not all genes that play a role in sex determination are Y-linked. The Y-chromosome, generally does not undergo genetic recombination except at small pseudoautosomal regions. The majority of the Y-chromosome genes that do not recombine are located in the "non-recombining region".