Birth Defect Terms and Definitions

Syndrome
The group or recognizable pattern of symptoms or abnormalities that indicate a particular trait or disease.

Mitosis
The process of nuclear division in cells that produces daughter cells that are genetically identical to each other and to the parent cell.

Deletion.
A loss of part of the DNA from a chromosome; can lead to a disease or abnormality.

Junk DNA
Stretches of DNA that do not code for genes; most of the genome consists of so-called junk DNA which may have regulatory and other functions.

Fraternal twin
Siblings born at the same time as the result of fertilization of two ova by two sperm. They share the same genetic relationship to each other as any other siblings.

Single-gene disorder
Hereditary disorder caused by a mutant allele of a single gene.

Genetic illness
Sickness, physical disability, or other disorder resulting from the inheritance of one or more deleterious alleles.

Birth defect
Any harmful trait, physical or biochemical, present at birth, whether a result of a genetic mutation or some other nongenetic factor.

Bacterial artificial chromosome (BAC)
A vector used to clone DNA fragments (100- to 300-kb insert size; average, 150 kb) in Escherichia coli cells.

Acquired genetic mutation
A change in the genetic structure that is neither inherited nor passed to offspring. Also called acquired mutations.