-Rare inherited disorder
- Mutations in the PAH gene cause phenylketonuria.
-Enzyme: Phenylalanine hydrase.
-Found in the liver
-Located on long arm of chromosome number 12 between positions 22 and 24

Thanks a Lot, Mom and Dad....

-Autosomal recessive mutation
-Must receive two mutated genes from both parties
-Won't develop if only one gene is passed, but child will become a carrier

The Culprit!

-Responsible for processing phenylalanine (building block of proteins)
-Change single amino acids. Most common: Arginine into triptophan at position 408.
-Also delete small amounts of DNA, causing gene disruptions.
-Makes tyrosine, which makes several hormones, melanin, and neurotransmitters.
-Large levels of phenylalanine can be very harmful to the brain, causing mental delay.

How Does PKU Work?

 Usually occurs when the enzyme phenylalanine hydroxylase is absent or severely
 Phenalalanine, an essential amino acid, cannot be broken down (and cannot be converted
into tyrosine)

 Accumulates in large quantities throughout the body

Symptoms of PKU

 Children with PKU appear normal at birth but develop mental retardation if not treated

 Tend to have lighter coloured skin, hair and eyes (unable to be converted into tyrosine,
which is involved with producing the melanin (pigment)
 Likely to have eczema and seizures
 Variety of neurological symptoms
 Musty-smelling sweat and urine (due to the byproduct phenylacetic acid)

Treatment for PKU

 Infants with PKU must be treated early; Symptoms irreversible if not treated early
 Untreated newborns develop between the ages three months and five months
 Screening phenylalanine levels in newborns to detect PKU before symptoms start to
develop (Analyze blood for phenylalanine concentration taken by pricking the heel of the
 Newborns should have a special low phenylalanine diet
 Diet avoids many natural foods, including breast milk (contain higher levels of
phenylalanine than PKU patients can tolerate)
 Diet may include low protein, natural foods, including fruits, vegetables, and some
 Ensure that normal levels are maintained by monitoring blood phenylalanine levels

 This diet must be used throughout the person’s life


  • Basic Research of Phenylketonuria (PKU). 2015. University of Southern California.
  • Güttler, Flemming, and Guldberg, Per(Aug 2011) Phenylketonuria. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0006027.pub2]
  • Learning About Phenylketonuria. (n.d.). Retrieved May 19, 2015, from
  • National Institutes of Health Consensus Development Conference Statement:Phenylketonuria: Screening and Management.
  • Phenylketonuria. (2014). In K. L. Lerner & B. W. Lerner (Eds.), The Gale Encyclopedia of Science (5th ed.). Farmington Hills, MI: Gale.

Comment Stream

2 years ago

Well done. Need one more literary journal article to meet rubric criteria. Don't forget to include in-text citations. Need references for your images as well. Formatting of text - needs some alignment TLC. Overall, well done.