Glossary of Terms

acquired
Not present at birth.

autosome
One of the non-sex chromosomes. There are 22 pairs of autosomes.

base
A component of DNA.

cardiac arrhythmia
An irregular heartbeat.

cell
The basic structural unit of most living things. Each cell typically contains an entire copy of an organism's genetic information.

chromosome
A microscopic, rod-like structure in the cell that carries genetic material.

DNA
Deoxyribonucleic acid; a double stranded molecule, organized as a double helix, which contains genetic information, primarily in the form of genes. There are four different bases in DNA: adenine (A), thymine (T), guanine (G) and cytosine (C). The order of these bases determines the function of the DNA.

electrocardiogram (ECG or EKG)
A recording of the heart’s electrical activity.

exon
A region of a gene that specifies a portion of a protein.

gene
A unit of heredity. Genes are composed of DNA (deoxyribonucleic acid).

genetic counselor
A professional trained to evaluate a family’s medical history to determine the presence of genetic disorders or other inherited traits and to assess the risk of these occurring in other family members.

genotype
the genetic make-up of an organism; the combination of alleles for a given loci

inherited
Passed through generations of a family, from parents to children.

mutation
A potentially harmful but rare change in the DNA sequence of a gene.

phenotype
A particular trait that is the result of environmental and genetic influences.

reduced penetrance
A term used to describe a genetic mutation for a dominant disorder whose effect is somehow modified so as not to cause symptoms when present in certain people.

sequence
The order, or arrangement, of the DNA bases that make up a gene.

sex chromosomes
The twenty-third pair of chromosomes. A sex chromosome can be either an X or a Y. The XX pair determines the female sex and the XY pair determines the male sex.

syncope
Fainting; loss of consciousness.

trait
Distinguishing characteristic.

variant
Any change in the sequence of a gene from what is most commonly found.

ventricle
A lower chamber of the heart. The human heart has two ventricles.

ventricular fibrillation
Rapid, irregular contractions in the heart's ventricles.

ventricular tachycardia
An extremely rapid heartbeat that begins in the heart's ventricles.

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