A Y-linked gene is a gene that is found on the Y chromosome, which is one of the two sex chromosomes in mammals. This gene is only present in males because females do not have a Y chromosome. There are several synonyms for the term Y-linked gene, including male-specific gene, Y chromosome gene, and holandric gene. These terms are used interchangeably to refer to genetic traits that are determined by the presence or absence of specific genes on the Y chromosome. Y-linked genes are particularly important in determining the male phenotype, including traits such as male fertility and the development of male reproductive organs.