Amino acid – The chemical unit that is the building block of proteins. Some examples are cysteine, valine, phenylalanine, guanine, aspartate
Ataxia – Uncoordinated movements
Athetoic movements – Writhing movements
Axon – Projection of a neuron (nerve cell) that carries nerve impulses from one cell body to another
Base – The chemical unit that is the building block of DNA (deoxyribonucleic acid); the four bases in DNA are adenine, thymine, guanine, cytosine, represented by the letters A, T, G, and C, that form the codons (three-letter words) of the genetic code
Benign – Not disease-causing
Carrier – A carrier has a disease-causing variant (mutation) on one chromosome of a pair and normal copy on the other chromosome of the pair. The normal copy compensates for the disease-causing variant and the person is not affected. Female carriers of a variant that causes PMD in males on one of their two X chromosomes are usually not affected. Males are not carriers because they only have one X chromosome.
Cell – A basic unit or building block that is able to perform all of the functions of life
Codon – A three-letter (base) “word” of the genetic code. A codon codes for one amino acid; for example, AGC codes for serine, which can be abbreviated Ser or S.
Connatal – Congenital; at birth
DNA – Deoxyribonucleic acid that contains the code for making proteins; forms a double-stranded helix
Dystonic posturing – A movement disorder with muscle contractions resulting in abnormal fixed postures.
Dysarthria – Slow speech
Exon – The exons are the part of a gene that are left in the RNA after splicing occurs, and they code for protein.
Gastrostomy – Surgery for the placement of a feeding tube
Hypotonia – Muscle weakness
Intron – The part of a gene that is spliced out of the RNA
Leukodystrophy – A disease of the white matter of the central nervous system (brain and spinal cord)
Magnetic resonance imaging (MRI) – A medical imaging technique that produces images of internal organs, such as the brain
Mutation – A base-change in the DNA; sometimes thought of as a disease-causing (pathogenic) change
Myelin – Fatty substance covering and insulating the axons of neurons so that nerve impulses travel properly from neuron (nerve cell) to neuron
Myelin sheath – Myelin that is wrapped around the axons of neurons (nerve cells) forming a covering
Neuron – Nerve cell
Nystagmus – Involuntary eye movements
Oligodendrocyte – Type of brain cell that produces myelin in its cell membrane and sends out projections of its cell membrane to wrap around axons of neurons (nerve cells) forming an insulating sheath
Pathogenic – Disease-causing
Protein – A chemical made of a chain of amino acids that provides a structural function or assists chemical reactions to occur in living things
RNA – Ribonucleic acid; transcription of the DNA code into RNA is an intermediate step between DNA and formation of protein
Spasticity – Tightness or stiffness of muscles
Splicing – Process by which introns are removed from RNA leaving the exons, which code for protein
Stridor – Characteristic sound of breathing when airflow is disrupted in the airway
Titubation – Head-bobbing
Variant – A base change; can be pathogenic (disease-causing) or benign (not disease-causing)
X-inactivation – The inactivation of genes on one copy of a pair of X chromosomes. Which of the two Xs is inactivated is usually random from cell to cell.