Birth Defect Terms and Definitions

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

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.

Risk communication
In genetics, a process in which a genetic counselor or other medical professional interprets genetic test results and advises patients of the consequences for them and their offspring.

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

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

Autosome
A chromosome not involved in sex determination.

Gene
The fundamental physical and functional unit of heredity. A gene is an ordered sequence of nucleotides located in a particular position on a particular chromosome that encodes a specific functional product

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

Pedigree
A family tree diagram that shows how a particular genetic trait or disease has been inherited.

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