Y-Linked traits in humans
Any gene that occurs exclusively on the Y chromosome is said to be holandric and it is not expressed in females. Such a Y-linked gene normally occurs in males and is transmitted only from father to son - holandric inheritance. Only a few Y-linked genes have been identified uptil now. One is the histocompatibility gene, known as the H-Y gene which is present on the short arm of the Y chromosome. Another important Y-linked gene is the TDF gene that codes for testis detprnining factor. This locus plays an important role in primary sex determination.
Another phenotype known to be associated with the Y chromosome is the condition hypertrichosis. The gene concerned with this condition leads to the developnlent of hairy pinna. This phenotype has been observed ill the inhabitants of Australia, Ceylon, Israel, and India.