Here's a breakdown:

* Autosomal recessive: This means the disorder is carried on a non-sex chromosome (autosome) and two copies of the faulty gene are needed for the disorder to manifest.

* Lack of enzyme: Individuals with PKU lack the enzyme phenylalanine hydroxylase (PAH).

* Amino acid phenylalanine: This is an essential amino acid found in protein-rich foods.

* Chemicals that...: Without PAH, phenylalanine builds up in the body. This leads to the formation of harmful byproducts that can damage the brain and nervous system, causing severe intellectual disability, seizures, and behavioral problems.

Key points about PKU:

* Early detection is crucial: Newborn screening programs are essential for diagnosing PKU.

* Dietary management: Individuals with PKU must follow a strict diet low in phenylalanine throughout their lives. This involves avoiding high-protein foods and consuming special formulas.

* Treatment: Early intervention and lifelong dietary management can significantly reduce the risks of PKU complications.

Let me know if you have any other questions.