Transmission of genetic disorders is by chromosomal or single gene inheritance. The risk of occurrence or recurrence of genetic disorders is predicted by studying the patterns of inheritance, based on the localization of genes on the autosomes or sex chromosomes. They are called autosomal or sex chromosomal disorders. Autosomal Dominant and recessive modes of inheritance are discussed. Mitochondrial mutations also may be responsible for degenerative disorders. They have a different mode of inheritance and are maternally inherited and expressed in both the sexes.