Genetics+Disorder-+PKU+DB

PKU- Phenylketonuria
•	**What causes it?: Talk about the gene mutation (and which chromosome the gene is on) and the misformed protein and how this causes the disorder.** PKU is an autsomal recessive disorder, meaning that both parents must carry the gene in order to pass it onto a child. The mutation of a single gene on chromosme 12 that causes PKU codes to make an enzyme. The enzyme, called the PAH enzyme, processes the protein phenylalanine. Without this enzyme, or with a low amount of it, phenylalanine builds up in the body and poisons neurons in the brain. The mutation of the gene causes the enzyme to change shape, work more slowly, or degrade.

•	**How is it inherited? Show a Punnett square or a pedigree and tell us if it is autosomal dominant, autosomal recessive, or X-linked recessive** The disorder is autosomal recessive, and two heterozygous parents have a 25% chance of having a child with the disorder. Both parents must carry the mutated gene for it to be passed on.





•	**How is it diagnosed?** All states now require a test of the blood phenylalanine level of newborns three days after birth. If a newborn is not screened however, it may be suspected if he or she has bluer eyes and fairer skin than other members of the family. More noticable symtoms typically appear after a few months and may include: vomitting, irrability, a musty odor in urine, and a skin rash. Increased muscle tone and reflexes may become apparent. More severe cases in all ages are also characterized by mental retardation, microcephaly (small head), seizures, and stunted growth.

•	**How is it treated?** Doctors recommend blood tests as children grow and throughout the life of a person with the disorder. A strict diet is advised, in which a person with PKU is to avoid phenylalanine-rich foods. These foods include all high-protein foods such as eggs, milk, beans, nuts, chicken, steak and fish. He or she should also avoid products with artificial sweeteners that include aspartame. The ingredient, found in diet sodas and some medications, causes the body to release phenylalanine and thus bring on symptoms of the disorder. People with PKU are limited to pasta, bread, rice, cookies and certain vegetables and fruits. The diet must be maintained and even fruits and vegetables must be eaten in moderation to avoid symtoms.



•	**What is it like to have it?** It can be difficulct and frustrating to have PKU. A person with PKU cannot eat the normal things that other get to eat and must plan ahead when going out with friends or to a restaurant. A person with PKU also has to have regular blood tests to monitor his or her phenylalanine level and must have doctors appointments as well. These tests, appointments and dietary requirements are not only a hassle but can become very expensive.

If PKU goes untreated though, irreversible brain damage will occur as well as social and developmental problems. Seizures and nervous system damage will make a person with untreated PKU irratible and uneasy.

(Show Video on "What is it like to have it?" Diets and Special Foods and Friends and Dating)

Sources - http://www.medhelp.org/lib/pku.htm - http://www.ygyh.org/pku/whatisit.htm - http://www.mayoclinic.com/health/phenylketonuria/DS00514/DSECTION=4