Find the definitions for the words in pink on the right.

What is PKU?

Phenylketonuria, or PKU, is a genetic disease inherited from a person's parents that affects the way a body processes phenylalanine (PHE), an amino acid in protein. Proteins found in food are first broken down into amino acids, which are then used to build the specific proteins that our bodies need. Phenylalanine is found in milk, cheese, eggs, fish, meat, beans, nuts, and infant formulas (both regular and soy), and also to a lesser extent in cereals, vegetables and fruit. People with PKU cannot break down phenylalanine into another amino acid, tyrosine. Phenylalanine then builds up in the bloodstream and causes brain damage. To avoid this, a person can eat a healthy diet that includes a low-phenylalanine formula, fruits, vegetables, sugars and other low-protein foods.

Who does PKU affect?

One out of 12,000 babies are born with PKU in the United States. Though anyone can get PKU, it occurs most often in people of Northern European ancestry. Out of all ethnic groups, Turkish people have the highest chance of getting PKU (one person in every 2600); one in 4500 Irish people have PKU. On the other hand, in African American, Ashkenazi Jewish, and Asian populations, PKU almost does not exist.

How will PKU affect my child?

A child with untreated PKU appears normal for his or her first few months. Between three and six months, a child with PKU will begin to lose interest in his surroundings. At a year, the child shows developmental delays and may be irritable, restless and destructive. Children with PKU are often mentally retarded. Also, they may have a small head size (microcephaly), or seizures, and many children have behavioral problems. Physically, children with PKU develop a "musty" odor caused by excessive phenylalanine. They tend to have dry skin and/or rashes. Children with PKU tend to have blonder hair and lighter skin (90% of people with PKU have blond hair and blue eyes) because phenylalanine is not broken down into tyrosine, a component of pigments.

Can I prevent my child from developing PKU?

No. However, negative effects from PKU can be prevented if you make sure that your child follows a special diet that is low in phenylalanine. The low phenylalnine diet consists of a special formula and foods that are naturally low in protein, such as fruits and vegetables. Specialty low-protein foods, such as flours, cookies, baked goods, and pastas that are modified to be low in protein, are also included in the diet. No high-protein foods are allowed. Aspartame (the sweetener in NutraSweet, Equal and other diet foods) must be avoided.

Your child should stay on a low-phenylalanine diet for his or her whole life. High levels of phenylalanine will lower his or her IQ, and cause learning and behavioral disorders. However, if your child follows a low-phenylalanine diet throughout his or her life, he or she will be able to learn and develop normally.

What is Maternal PKU?

There are about 5,000 healthy young women of childbearing age with successfully treated PKU in the Unites States today; about 300 of mothers with PKU give birth a year. The mothers have developed normally, have normal IQs, and lead normal lives. Many ended the special diet in early childhood, which had been the recommended policy in most clinics until the 1990s. Thus, they do have high blood phenylalanine levels. THIS IS BAD for a developing baby. High phenylalanine levels cause mental retardation (95% of the time), small head size, or microcephaly (90%), leading to developmental delays, brain damage, and lower IQ's, among other things, or heart disease (17%), even if the child does not have PKU. Most of the children who are born to mothers with high PHE levels will not inherit PKU.

If a woman with PKU follows the low-protein diet early enough in her pregnancy, maintains the diet throughout her pregnancy, and closely monitors her blood levels, she can reduce the risks associated with maternal PKU.

How did my child develop PKU?

Every person has two genes that can cause PKU, one gene that was inherited from the father and one that was inherited from the mother. Each gene either carries PKU or it is normal. If both parents pass along the normal gene, then the child will not have PKU and will not be a carrier. If one parent passes along a PKU gene, but one parent passes along a normal gene, then the child does not have PKU. (One in every 50 people are carriers, people who have a PKU gene.) For PKU to develop, both parents must carry the gene, and both must pass along the gene. This method of inheritance is termed autosomal recessive.

a building block of protein. There are two types of amino acids: non-essential and essential. Essential amino acids (like PHE) cannot be produced in the body and must be ingested through the diet. Non-essential amino acids are produced by the body, and therefore do not have to be eaten.

a way of classifying inheritance when there are only two genes involved in a trait. An autosomal recessive trait will not show up unless both genes are recessive; when a person inherits one recessive gene from a parent, but a normal gene from the other parent, that person is considered a carrier of the trait.

when a person has inherited one recessive gene from a parent but has a normal gene from the other. The normal, or dominant, gene covers up the recessive gene and keeps it from appearing in the body. The person is considered a carrier, though, because he or she may pass the recessive gene on to a child when conceiving. If two carriers pass their recessive genes on, the trait will appear in their offspring.

the body's means of storing genetic information. Genes tell the body how to operate by making specific proteins. A person inherits half of his or her genes from his or her mother and half from his or her father. Genes may be dominant or recessive. Traits associated with dominant genes will always show up, whereas traits linked to recessive genes will only appear if no dominant genes are present. PKU occurs when two recessive genes are inherited.

(mPKU) refers to when a woman with PKU becomes pregnant. If untreated, mPKU leads to mental retardation, etc. because the mother had high levels of PHE in her blood while pregnant. The child will not necessarily have PKU, but it will suffer from symptoms of maternal PKU.

a condition where an infant has a smaller head than normal. It may cause a delay in motor skill development, mental retardation and hyperactivity.

an abbreviation for Phenylalanine

(PHE) an essential amino acid found in protein. People with PKU cannot break down PHE into Tyrosine, and so it builds up in the bloodstream.

an essential ingredient for any living thing. Proteins are made up of amino acids and do basically everything and anything in the human body: they serve as building materials, chemical messengers, regulators of chemical reactions, etc.

(TYR) a non-essential amino acid that is formed when PHE is broken down. In a person with PKU, TYR is actually an essential amino acid because that person's body cannot produce it on its own.