Holandric (Y-linked) Inheritance

Holandric inheritance refers to the inheritance of genes located on the Y chromosome. Since only males possess a Y chromosome (XY), these traits are passed directly from father to son.

Key Characteristics

Male-to-Male Transmission: A father will pass a holandric trait to all of his sons, but none of his daughters (as daughters receive his X chromosome).

• No Dominance/Recessiveness: Because males have only one Y chromosome, the concept of “dominant” or “recessive” doesn’t apply in the traditional sense; if the gene is present on the Y, the trait will be expressed.
• Limited Traits: The Y chromosome is relatively small and contains fewer genes compared to the X chromosome, so holandric traits are quite rare.

Classic Example

Hypertrichosis Pinnae: A condition characterized by excessive hair growth on the outer rim of the ear. While historically cited as a classic holandric trait, modern genetics suggests it may be more complex, though it remains the textbook example for many exa