Why is sex-linked inheritance an example of nonmendelian inheritance?
The Sex-linked inheritance is a kind of nonmendelian inheritance because it opposes Mendel's first law, which postulates that each trait is always conditioned by two factors (alleles). In the nonhomologous regions of the sex chromosomes the genotypes of the genes contain only one allele (even in the case of the XX karyotype that is in women, one of the X chromosomes is inactive).