PKU

Inheritance	autosomal recessive
Occurrence	1 in 18,000
Description	individuals with PKU cannot digest the amino acid phenylalanine (part of many proteins)-- levels of phenylalanine rise in the bloodstream and cause brain damage
Testing for PKU	The diagnostic test for PKU is one of the few standard procedures administered to all newborns. It involves the pricking of the baby's heel to draw blood and then measuring the levels of phenylalanine.
Treatment for PKU	When diagnosed in newborns, PKU is treated by having the child eat a special diet where foods either have no phenylalanine or very low levels of phenylalanine. When the diet is properly administered, brain damage and mental retardation can be prevented.

All about PKU

PKU can be introduced to students during several different units: first, when your students are learning translation and understanding how the genetic code places amino acids in order to create proteins, second, when discussing nutrition and the need for protein in our diets, and third, when studying Mendel and teaching about recessive traits.

Here are some questions that could test students' understanding of some of the topics above.

(1) If a phenotypically normal couple finds out their first child has PKU, what is the probability that their next child will also have PKU? 25%

(2) If an individual is a carrier for PKU and marries a homozygous normal spouse, what is the probability that they will have children who have PKU? 0%

(3) If an individual is a carrier for PKU and marries a homozygous normal spouse, what is the probability that they will have children who are carriers for PKU? 50%

(6) What amino acids are coded by the following mRNA strand? If you had PKU would you eat this protein?

met------thr-------ser-------cys-------arg------phe-----leu------phe------phe------phe-----stop

PKU (Phenylketonuria)

All about PKU