: The genes for X-linked or diandric sex-linked characters lie on the nonhomologous part of the X-chromosome. They do not have their allele on Y-chromosome. The genes of these characters are transferred from father to daughter and from daughter to her son. This is termed as criss-cross inheritance. Sons receive these characters from mother only while daughters receive from mother and father both e.g. colourblindness, haemophilia.