noun, plural: sex-linked traits
A sex-linked trait is a trait that is controlled by a gene or an allele located on the sex chromosome. In humans, the sex chromosomes are the X chromosome and the Y chromosome. A trait that is determined by the allele on X chromosome is particularly described as X-linked whereas that determined by the allele on Y chromosome is said to be Y-linked.
Since traits are sex-linked, there is usually a distinct pattern. Some traits would therefore be linked to the sex or gender of an individual. The manifestation of certain traits as an outcome of the expression of particular genes in the sex chromosome is referred to as sex linkage. For example, color blindness is a sex-linked trait whose allele is recessive and located on the X chromosome. When the mother is color blind and the father is not, all sons are going to be color blind. The daughters are going to be normal but carriers of the gene. Conversely, when the father is color blind and the mother is not, all sons and daughters are normal but the daughters will be carriers of the gene.