Sex Linked Inheritance

A sex-linked trait is any trait whose gene sits on one of the sex chromosomes rather than on an autosome, and its inheritance pattern is called sex-linked inheritance. Genes located in the differential (non-homologous) region of the X chromosome — the part of X that has no matching counterpart on Y — are called X-linked genes; genes in the differential region of the Y chromosome, with no counterpart on X, are called Y-linked or holandric genes. Because these differential-region genes on X and Y have nothing to pair with on the other sex chromosome, they cannot undergo crossing over during meiosis the way genes on the autosomes or on the shared pseudoautosomal regions can — an X-linked allele and a Y-linked allele are essentially locked to their own chromosome for the rest of that lineage. …