A
Adenine: One of the four bases that make up DNA. Abbreviated with an 'A'.
Amino acid: The type of molecule found inside proteins. Phenylalanine is one kind of amino acid.
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B
Bacterial inhibition assay: A common screening test for PKU, developed by Guthrie and Susi in 1963.
Base: One of the molecular components of DNA. Bases - A, C, G, and T - are arranged in line in a DNA molecule (e.g., CGGTACAGG) and encode instructions for making proteins.
BH4: A molecule that helps the PAH enzyme convert phenylalanine to tyrosine. About 2% of people with phenylketonuria accumulate excess phenylalanine because BH4 doesn't work properly.
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C
Carrier: A person that carries a gene that causes a disorder, but does not show symptoms.
Cerebral cortex: The thin layer of gray matter covering the surface of the brain. Nerve cells in the cerebral cortex are involved in movement, perception, and memory.
Chromosome: Chromosomes are packages of DNA found in the nucleus of cells. Humans have 46 chromosomes.
Cytosine: One of the four bases that make up DNA. Abbreviated with a 'C'.
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D
Dopamine: A chemical sent by one neuron to another that allows neurons to communicate messages to each other.
DNA: Short for deoxyribonucleic acid, DNA is the molecule that carries genetic information.
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E
Endoplasmic reticulum: Organelle inside the cell where proteins are produced.
Enzyme: A protein that helps other chemical reactions in the body proceed.
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G
Gel: Hard Jello-like substance that scientists use to measure the size of DNA fragments during DNA diagnostic tests.
Gene: A portion of DNA that contains instructions for making a protein.
Genotype: The genetic composition of a person. Usually used when considering one gene or chromosome (e.g., males have a XY genotype, females have a XX).
Guanine: One of the four bases that make up DNA. Abbreviated with a 'G'.
Guthrie card: Paper used to collect a blood sample from a newborn child for screening tests.
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M
Mutation: A change in the genetic code (the A's, C's, G's and T's) of a gene.
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N
Neuron: A type of cell in the brain. Neurons receive signals from the outside, process signals, and send information to other neurons, muscles, or glands.
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P
PAH: An enzyme in the liver that converts phenylalanine to tyrosine. PAH stands for phenylalanine hydroxylase. PAH is missing in people with PKU.
PCR/Polymerase chain reaction: A method to increase or amplify specific sequences of DNA. This method can be used to detect changes in DNA sequence that cause genetic disorders.
Phenylalanine: An essential amino acid that we absorb from protein we eat. Our bodies use phenylalanine, along with 19 other types of amino acids, to construct our own proteins. Excess phenylalanine is toxic and is usually converted to non-toxic tyrosine.
Phenylketonuria: A recessive disorder that results from the inability of the body to convert phenylalanine to tyrosine. Usually this inability is caused by a deficiency in the PAH enzyme. Abbreviated PKU.
PKU: A recessive disorder that results from the inability of the body to convert phenylalanine to tyrosine. Usually this inability is caused by a deficiency in the PAH enzyme.
Protein: A type of molecule produced by the body from smaller molecules called amino acids. The instructions for producing proteins reside in the genes.
Punnett square: A method of showing the potential offspring of two parents.
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R
Recessive: Refers to genetic disorders in which a person must have two copies of the mutated gene to develop the disorder.
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T
Thymine: One of the four bases that make up DNA. Abbreviated with a 'T'.
Tyrosine: An amino acid that is absorbed from protein we eat, and that is obtained from phenylalanine through an enzymatic reaction. People with PKU cannot convert phenylalanine to tyrosine.
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W
White matter: A material called myelin that is wrapped around some nerve cells. Myelin quickens the transmission of an electrical impulse through the cell.
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