Y linkage

In mammals, Y-linkage, also known as holandric inheritance, is the determination of a phenotypic trait by an allele (or gene) on the Y chromosome.

Because the Y-chromosome is small and does not contain many genes, few traits are Y-linked, and Y-linked diseases are rare. Since the only humans who have a Y chromosome are males, Y-linked traits are passed only from father to son, with no interchromosomal genetic recombination.

Y-Chromosome deletions are a frequent genetic cause of male infertility. Having hairy ears was once thought to be a Y-linked trait in humans, but that hypothesis has been discredited.

Genes known to be contained on the Y chromosome
As of the year 2000, a number of genes were known to be Y-linked, including:
 * ASMTY (acetylserotonin methyltransferase),
 * TSPY (testis-specific protein),
 * IL3RAY (interleukin-3 receptor),
 * SRY (sex-determining region),
 * TDF (testis determining factor),
 * ZFY (zinc finger protein),
 * PRKY (protein kinase, Y-linked),
 * AMGL (amelogenin),
 * CSF2RY (granulocyte-macrophage, colony-stimulating factor receptor, alpha subunit on the Y chromosome),
 * ANT3Y (adenine nucleotide translocator-3 on the Y),
 * SOX21 (known to cause baldness),
 * AZF2 (azoospermia factor 2),
 * BPY2 (basic protein on the Y chromosome),
 * AZF1 (azoospermia factor 1),
 * DAZ (Spermatogenes is deleted in azoospermia),
 * RBM1 (RNA binding motif protein, Y chromosome, family 1, member A1),
 * RBM2 (RNA binding motif protein 2), and
 * UTY (ubiquitously transcribed TPR gene on Y chromosome).
 * USP9Y
 * AMELY