How the transmission of linked genes is different when present on homologous and non-homologous regions of sex chromosomes?

Explanation

(1) Sex chromosomes, X and Y show homologous and non- homologous regions. The genes present on the homologous regions are similar while those on non-homologous regions are dissimilar.
(2) Genes present on non-homologous regions of X and Y chromosomes are respectively called, X-linked and Y-linked genes. They are called completely sex-linked genes.
(3) The sex-linked genes are inherited together as crossing over does not occur in these regions of sex chromosomes.
(4) X-linked genes are expressed in both the sexes while Y-linked genes are expressed only in males. E.g. Genes for red-green colour- blindness, haemophilia, etc. are situated on the non-homologous region of X-chromosome. Hypertrichosis gene is located on non- homologous region of Y-chromosome. These genes are called completely sex-linked genes.
(5) The genes located on the homologous regions of X- and Y- chromosomes are called incompletely sex-linked genes.
(6) They do not get inherited together because crossing over may take place in such regions of sex chromosomes. E.g. Genes for nephrities and total colour blindness are situated on the homologous regions of X- and Y-chromosomes and hence they are called incompletely sex-linked genes.