PKU is human hereditary disease where the body fails to process phenylalanine found in protein we intake in our daily food. It is caused by recessive allele of simple Mendelian inheritance. It os causes when father and mother are heterozygotes. Solution PKU is human hereditary disease where the body fails to process phenylalanine found in protein we intake in our daily food. It is caused by recessive allele of simple Mendelian inheritance. It os causes when father and mother are heterozygotes..