Explaining the link

• An example of a disorder used to explain the difference is called PKU
• Phenylketonuria (PKU) is a deficiency in the enzyme (PAH), which is found in dairy
• PKU is a recessive genetic disorder (this means PKU only appears when 2 parents have the recessive gene
• If only one parent has the gene, it is possible the child may not inherit the disorder
• If undetected or untreated at birth, children can fail to accomplish important developmental milestones
• However, if PKU is diagnosed early, a baby can develop normally if given a special diet, low in phenylalanine for the rest of their life.
• This shows how the genotype and the environment link