The image above shows how Phenylketonuria can be
 passed/inherit from parents to offsprings.











This image above  shows how the building up of Phenylalanine
turns into toxic levels that a kid cannot handle & can't produce the 
amino acid, Tyrosine.


I've learned that the cause of Phenylketonuria may be
caused from a single mutation.
That may have had occurred in Chromosome 12.
Different mutations have different effects on the enzyme.
Some mutations change the shape of the enzyme
so that in no longer recognizes Phenylalanine anymore.
Some mutations change the shape so that the
enzyme works very slowly.
Other mutations change the shape so that the enzyme 
is unstable & degrades.


If a person with PKU keeps adding Phenylalanine 
foods into his /her body .
Phe builds up in the brain & poisons the neurons.